Saturday was the Yankees’ first official summer workout, a routine bit of preparation to start their coronavirus-shortened 2020 season. Instead of an ordinary practice at Yankee Stadium, the team witnessed a frightening incident in which a key pitcher was hit on the head with a line drive. And later in the day, it announced that two other players were absent from practice because they had tested positive for Covid-19.

Masahiro Tanaka, a two-time All-Star, lay motionless on the ground after being struck with a ball off the bat of his teammate, the slugger Giancarlo Stanton. Tanaka eventually sat up and walked off the field with two athletic trainers by his side. He was released from NewYork-Presbyterian Hospital on Saturday night after being evaluated for concussion-like symptoms.

The Yankees also announced positive tests for star infielder D.J. LeMahieu and pitcher Luis Cessa with their permission, as league rules prevent teams from naming players without consent.

LeMahieu and Cessa remain isolated at their homes and will need to test negative before traveling to New York to join the team, Yankees Manager Aaron Boone said. LeMahieu has been asymptomatic, while Cessa has shown “very mild” symptoms of the virus.

“We’ll see how that continues to unfold the next several days,” Boone said.

Tanaka, who returned to his native Japan soon after the season had been suspended in mid-March because of the coronavirus pandemic, was facing a pair of Yankees power hitters, Aaron Judge and Stanton, at Yankee Stadium on Saturday afternoon as he threw in front of coaches for the first time in months.

But Tanaka had little time to react when Stanton, who hits the ball as hard as anyone in baseball, drilled a line drive toward the mound. The ball struck the right-handed Tanaka on the right side of the head, knocking him to the ground, where he lay for at least five minutes while cradling his head.

“It sucks to see something like that, especially during something as simple as a sim game,” outfielder Aaron Hicks said in a video news conference with reporters.

After the ball hit Tanaka, Stanton immediately crouched down and put his hand on his helmet, seemingly upset that he had hit hurt his teammate. With the Miami Marlins in 2014, Stanton sustained facial fractures and needed multiple dental procedures when he was hit in the left cheek by a pitch from Mike Fiers, then with the Milwaukee Brewers.

“It’s incredibly unfortunate what happened today,” Boone said. “In a lot of ways, we’re hopeful we avoided something really bad happening.”

Tanaka, 31, is in his final season of a seven-year, $155 million contract he signed with the Yankees before the 2014 season, in which he was selected as an All-Star. He was also an All-Star in 2019, a season in which he posted a 4.45 earned run average over 182 innings.

Tanaka had been pitching without a so-called L screen, a protective barrier often used during practice sessions. But after seeing Tanaka get hurt, pitcher Jordan Montgomery said he was so shaken up that he requested one, which he had not originally planned on using.

“It’s horrible,” Montgomery said, adding later: “I hope he’s OK. I’m thinking and praying for him right now.”

Last year, the Yankees set a major league record with 30 players spending time on the injured list.

Two undefeated horses trained by the Hall of Famer Bob Baffert indeed tested positive for a banned substance in Arkansas, a person familiar with the results of the split-sample test said Monday.

One of the horses, Charlatan, won a division of the Arkansas Derby on May 2. The other, a filly named Gamine, won the Acorn Stakes at Belmont Park in New York on June 20 by nearly 19 lengths in a stakes-record time of 1:32.55, a performance that inspired talk of the filly taking on the boys in the Kentucky Derby, which is scheduled for Sept. 5.

The horses had two samples test positive for lidocaine, a local numbing agent, according to the person who spoke on condition of anonymity because the case had not been fully adjudicated. The New York Times reported on the positive tests of their first samples in late May.

The anesthetic is considered a Class 2 drug by the Association of Racing Commissioners International, and use of it carries a penalty of a 15- to 60-day suspension and a fine of $500 to $1,000 for a first offense. In the absence of mitigating circumstances, the horse would also be disqualified and forfeit its purse. Charlatan earned $300,000 for first place in one of two top races at the Arkansas Derby.

Baffert, who had exercised his right to have a second test performed, planned to dispute the findings and argue that the positive tests were a result of environmental contamination by one of his employees, said Baffert’s attorney, W. Craig Robertson III.

“This is a case of innocent exposure and not intentional administration.” Robertson said in a statement.

ImageGamin, right, a filly ridden by John Velasquez, won the Acorn Stakes at Belmont Park in New York on June 20.Credit…Victor J. Blue for The New York Times

Lidocaine can be used legitimately for suturing wounds or as a diagnostic tool to determine whether horses are sound enough to compete. The drug may also be present in ointments or creams used on cuts or abrasions. It is regulated because of its potential to mask lameness in an unsound horse.

Officials from the Arkansas Racing Commission did not answer phone calls from The Times. In May, however, Alex Lieblong, the chairman of the Arkansas Racing Commission, told The Times it would schedule a hearing as soon as the second test came back.

“When we get it, there will be no delaying tactics,” he said. “Anything we can expedite, we will do.”

Four days after Charlatan’s runaway victory in the $500,000 Arkansas Derby, the colt’s stallion rights were sold for an undisclosed sum to Hill ‘N’ Dale Farm. The colt missed the Belmont Stakes with an ankle injury, and Baffert has said he will miss the Kentucky Derby, as well. Charlatan may be able to come back in time for the Preakness on Oct. 3.

Justify, another horse trained by Baffert, failed a drug test after winning the Santa Anita Derby, nearly a month before the 2018 Kentucky Derby. Justify wound up sweeping the Derby, Preakness and Belmont Stakes that year for the Triple Crown. The rule on the books when Justify failed the test required that the horse be disqualified, forfeiting both his prize money from the Santa Anita Derby and his entry into the Kentucky Derby.

California racing officials investigated the failed test for four months, allowing Justify to keep competing long enough to win the Triple Crown. In August, after Justify’s breeding rights had been sold for $60 million, the California Horse Racing Board — whose chairman at the time, Chuck Winner, had employed Baffert to train his horses — disposed of the inquiry during a rare closed-door session.

The board ruled that Justify’s positive test for the banned drug scopolamine had been the result of “environmental contamination,” not intentional doping. Baffert has denied any wrongdoing, but the quantity of the drug found in Justify suggested that it was present not because of contamination in his feed or his bedding but rather because of an effort to enhance performance, according to Dr. Rick Sams, who ran the drug lab for the Kentucky Horse Racing Commission from 2011 to 2018.

Mick Ruis, the owner of the second-place horse in the Santa Anita Derby, is in litigation with California officials to have his colt Bolt d’Oro declared the winner and awarded the $600,000 first-place check.

In March, federal prosecutors announced the arrests of 27 people, including veterinarians and drug distributors, charging them in a series of indictments with doping racehorses and cheating the public. Among those charged was Jason Servis — who trained Maximum Security, the horse that crossed the finish line first in the 2019 Kentucky Derby but was disqualified for interference.

Major League Baseball triumphantly declared on Monday morning that it would announce a 60-game schedule on its cable network that evening. Around the same time, the two teams from last year’s World Series, the Washington Nationals and the Houston Astros, were canceling their Monday workouts for safety reasons — and blaming M.L.B.

The reason for the holdup was a delay in receiving the results of the coronavirus tests both teams took on Friday. The Oakland Athletics’ tests, too, had not even been delivered to the M.L.B. laboratory in Utah as of Sunday night. The St. Louis Cardinals also canceled their workout Monday because of the testing delay.

The first few days of “2020 Summer Camp presented by Camping World” have been a disaster, the official sponsor all but inviting you to head for the wilderness, pitch a tent, curl up in a sleeping bag and sleep off the storm.

“The season, it’s not on my radar, really,” Brewers Manager Craig Counsell told reporters in Milwaukee. “This is on my radar: It’s keeping everybody healthy and safe and doing the best we can at that job.”

Like other industries in the United States, M.L.B. is trying to find its way in the grim new reality of pandemic life. The coaches and some players wear masks, news media access is severely limited and everyone practices social distancing as much as possible. There is no recent blueprint to follow, no foolproof protocol for administering nearly 4,000 tests last week. Mistakes were inevitable.

But failing to properly plan around holiday weekend delivery issues is hard to excuse, and it has given the players yet another reason to distrust Commissioner Rob Manfred. We saw this dynamic highlighted across three exasperating months of failed negotiations on restarting the season. Now, even team executives are livid with the league.

“We will not sacrifice the health and safety of our players, staff and their families,” Nationals General Manager Mike Rizzo said in a statement on Monday. “Without accurate and timely testing, it is simply not safe for us to continue with summer camp. Major League Baseball needs to work quickly to resolve issues with their process and their lab. Otherwise, summer camp and the 2020 season are at risk.”

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In a statement Monday afternoon, M.L.B. defended its testing process by saying that more than 95 percent of its planned tests had been conducted and analyzed. “We have addressed the delays caused by the holiday weekend and do not expect a recurrence,” it said.

The players will be tested, as planned, every other day through the end of the World Series, and bad news has already been pouring in. Atlanta’s Freddie Freeman, Colorado’s Charlie Blackmon, Kansas City’s Salvador Perez, San Diego’s Tommy Pham, Texas’ Joey Gallo and the Yankees’ D.J. LeMahieu are among the many players who have tested positive for the coronavirus.

ImageFreddie FreemanCredit…Joe Robbins/Getty ImagesImageCharlie BlackmonCredit…Ross D. Franklin/Associated Press

Freeman’s wife, Chelsea, wrote on Instagram Sunday that her husband had experienced body aches, headaches, high fever and chills for several days, despite the family’s strict adherence to social distancing. Freeman’s experience was sobering for his teammate, outfielder Nick Markakis, who announced Monday that he would opt out of playing this season.

“I talked to Freddie Freeman the other day, and just hearing the way he sounded over the phone kind of opened my eyes,” Markakis, 36, told reporters on Monday. “Freddie didn’t sound good. I hope he’s doing good, I hope he’s healthy, I know these guys need him more than anybody. Just to hear him, the way he sounded, it was tough.”

Markakis added that he has three children and has already missed much of their youth. Given his teammate’s ordeal, and the prospect of playing in empty stadiums, Markakis said goodbye.

“We play for the fans, and to take them out of the equation, it’s tough, and I think that was kind of the blow for me,” Markakis said. “I knew coming into it, but until you actually get into the situation and you go there and experience it, it changes things. I love the game. I hate to see it the way it’s going right now, but that’s the way things have to be.”

In opting out, Markakis joined a list of players that includes two former Cy Young Award winners — David Price of the Los Angeles Dodgers and Felix Hernandez of the Braves — plus veteran mainstays like Ian Desmond of the Colorado Rockies, Mike Leake of the Arizona Diamondbacks and Ryan Zimmerman of the Nationals. All of them, like Markakis, have earned more than $90 million in their careers. The risk, for a two-month season, was simply not worth it.

ImageFelix HernandezCredit…Brynn Anderson/Associated PressImageNick MarkakisCredit…Curtis Compton/Atlanta Journal-Constitution, via Associated Press

Of course, the virus threatens everyone, regardless of salary. Nationals pitcher Joe Ross, who has earned less than $4 million in his career, also opted out. His teammate, the cerebral reliever Sean Doolittle, framed the issue eloquently in a Zoom conversation with Washington reporters on Sunday.

“We’re trying to bring baseball back during a pandemic that’s killed 130,000 people,” Doolittle said, as reported by The Washington Post. “We’re way worse off as a country than we were in March when we shut this thing down. And, like, look where the other developed countries are in their response to this. We haven’t done any of the things that other countries have done to bring sports back.

“Sports are like the reward of a functioning society. And we’re trying to just bring it back, even though we’ve taken none of the steps to flatten the curve.”

The Chicago Cubs’ Kris Bryant said he would play, but was dismayed by the lag time in testing results.

“I wanted to play this year because I felt that it would be safe and I would be comfortable — honestly, I don’t really feel that way,” Bryant told Chicago reporters on Monday, adding later, “If we can’t nail the easy part, which is right now and just our players, we’ve got a big hill to climb.”

ImageKris Bryant during a workout at Wrigley Field on Sunday. “We’ve got a big hill to climb,” he said of the difficulties in safely completing a season.Credit…Patrick Gorski/USA Today Sports, via Reuters

Indeed, baseball has not even gotten to the most ambitious part of its plan: staging games at all 30 ballparks, with travel in between, while the virus still rages. The league is counting on every player — and anyone they interact with, at home and on the road — to strictly follow all safety protocols. Yet the league itself has already bungled the early stages of testing.

If you were an older coach, would you take the risk? One of the younger ones, the Cubs’ Tommy Hottovy, 38, contracted the virus during M.L.B.’s absence and struggled for a month with a fever, shortness of breath, sleepless nights and depression. Some older coaches are working remotely, like the Mets’ Chili Davis, 60; the Kansas City Royals’ Rusty Kuntz, 65; and the Seattle Mariners’ Perry Hill, 68. Others trust the league to keep them safe.

“I know you can do everything right and still get this virus, but I know also that if you’re doing things right, your percentages go way down,” said Boston Red Sox Manager Ron Roenicke, 63, adding later, “Nobody knows exactly what the right thing is to do, but I think Major League Baseball is doing the best we can in trying to get this game going again.”

Maybe so. But if this is the best M.L.B. can do, the season is doomed.

FC Dallas pulled out of Major League Soccer’s tournament in Florida after 10 players and a staff member tested positive for the coronavirus, M.L.S. officials announced on Monday.

The positive tests appeared after the team arrived in Orlando, Fla., on July 1, where the tournament starts July 8 at the ESPN Wide World of Sports Complex at the Walt Disney World Resort. All of the team’s players, coaches and staff were quarantining in their rooms as of July 4, according to The Associated Press.

Three players from two other teams also tested positive for the virus, bringing the total to 13 out of 557 players in Orlando. The remaining 25 clubs are set to compete in the monthlong tournament in one of the first professional sports to return to competition. The N.B.A. and W.N.B.A. are set to hold similar tournaments in Florida later in July.

“Given the impact of the number of positive tests on the club’s ability to train and play competitive matches, we have made the decision to withdraw FC Dallas from the M.L.S. is Back Tournament,” M.L.S. Commissioner Don Garber said in a statement.

The PGA Tour’s Memorial Tournament, scheduled next week in central Ohio, had hoped to pave the way for spectators to return to golf events during the coronavirus pandemic, and in turn perhaps provide a blueprint for how fans could safely attend other major American sports competitions.

But on Monday, the tour and tournament organizers announced they were scrapping plans to allow as many as 8,000 fans per day at the event. The rise in Covid-19 cases nationwide, and in Ohio, were the primary factors in the decision.

“While we embraced the opportunity to be the first PGA Tour event to welcome the return of on-site fans — and be a part of our nation’s collective re-emergence from the Covid-19 crisis, we recognize the current increase in positive Covid-19 cases across the country, and our ultimate responsibility,” Dan Sullivan, the tournament’s executive director, said in a statement.

Jay Monahan, the tour commissioner, referred to “the broader challenges communities are facing,” and said the focus was now on “the health and safety of all involved.”

In recent weeks, several PGA Tour players and their caddies have tested positive for the virus, which has caused a handful of elite golfers to withdraw from tournaments.

The Memorial, hosted since the mid-1970s by Jack Nicklaus and set to begin on July 16, is one of the tour’s featured events and always boasts a strong field of top golfers. It is one of Tiger Woods’s favorite events, which he has won five times. Woods, who has not played on the PGA Tour since February, is expected to make his return to the circuit at next week’s tournament.

Since June, the Memorial Tournament had the approval of state and local officials for a limited number of spectators — about 20 percent of the usual capacity — at the Muirfield Village Golf Club in Dublin, Ohio. Grandstands and bleachers were not constructed but fans, under specific social distancing guidelines, would have been allowed to watch the competition from various viewing sites on the grounds.

So far, the PGA Tour has held four fan-free tournaments. More than 20 other events are scheduled in 2020, though none currently expect to host fans on-site. That includes the P.G.A. Championship, the first golf major of the season, which will be held in San Francisco from Aug. 6 to 9.

Monahan, in a statement Monday, said that the tour would welcome fans, “when the time is right.”

The quaint old emblem is everywhere at Fenway Park, from the Green Monster to the roofs of the dugouts to the exit ramps in the grandstand: two stockings, one snugly overlapping the other, the symbol of the Boston Red Sox for generations.

On Friday, though, when the players arrived for the first summer workouts of a surreal season, the logo looked different on the signs above the bullpens and near the home bench. The little red socks dangled apart from each other, and accompanying messages implored players to practice social distancing.

The official anthem of the 2020 season might as well be “Don’t Stand So Close to Me,” by the Police. Nobody’s taking you out to the ballgame anytime soon.

“It’s never going to be a risk-free environment, we know that,” Red Sox pitcher Collin McHugh said. “That’s the environment we know we’re coming back to play in.”

Major League Baseball plans to open its 60-game season on July 23, with no fans in the stands because of the coronavirus pandemic. The league is essentially preparing a three-month television series, with 30 ballparks as studios and no live audiences. Rehearsals are officially underway, with a notable wardrobe addition for anyone working with the players.

“When you see all the smiles on their faces, it’s a good thing,” Red Sox Manager Ron Roenicke said. “I know you can’t really see the smiles on us, because we’ve got our masks on. But it was a long time at home.”

ImageChristian Vazquez, left, chatted with Kevin Plawecki over a Fenway Park wall during the first official workouts of the summer.Credit…Adam Glanzman/Getty Images

It was essentially another off-season, an unplanned, three-and-a-half-month break after a month of spring training. Some Boston players have tested positive for the coronavirus, Roenicke said, though he could not say how many. The team’s best starting pitcher, Eduardo Rodriguez, is awaiting results of a test; he did not go to Fenway on Friday because he has recently been in contact with someone who is sick.

“Eddie was fine with me telling you guys that, but I just don’t want to have to talk about this every day, because it’s going to come up every day,” Roenicke said on a Zoom call with reporters, who remained separated from players and staff members at the stadium. “We’re tested all the time.”

M.L.B. and the players’ union announced the results of the first round of that testing on Friday: Out of 3,185 tests, 38 were positive (31 players and seven staff members). Eleven clubs had no positive tests among their ranks.

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Because of health privacy laws, teams need players’ permission to disclose their presence on the new Covid-19 injured list. But if a player is missing and the team will not say why, it may not be hard to guess the reason.

ImageChaim Bloom, Boston’s chief baseball officer, was one of the few staff members to mingle among the players and coaches.Credit…Adam Glanzman/Getty Images

“We have to be extremely vigilant about making sure that we follow these health and safety protocols we’ve been working toward for three months,” said McHugh, a member of the players’ union’s executive committee. “I think some positives are to be expected; guys are coming from different parts of the country, different parts of the world.”

The Red Sox worked out in shifts on Friday — pitchers and catchers in the morning, others in the afternoon — and while the players were unmasked, they were generally spread out. Reporters watched from the fifth-level press box; photographers shot from the stands.

Besides Chaim Bloom, Boston’s chief baseball officer, who wore a mask and kept his distance, few staff members mingled among the players and coaches.

With as many as 60 players allowed in each major league team’s camp — and only one diamond, of course — clubs will utilize other local facilities for overflow. Some Red Sox, for example, will work out at Boston College starting Saturday.

ImageA masked Ron Roenicke, left, watched as Alex Verdugo took batting practice. Credit…Michael Dwyer/Associated Press

Coordinating the plans, while keeping in regular contact with players from a distance, has been exhausting for Roenicke, who has been in baseball since 1977. He called this the busiest he has ever been.

“We tried to provide as much guidance as we could through phone calls and Zoom calls and texts; certain guys were able to share some pitch data with me,” the pitching coach Dave Bush said. “But a big part of baseball is the hands-on, face-to-face interaction, just on a personal level and also a coaching level. I’m very happy to be back around people.”

The comforting sounds were all back on Friday — the crack of the bat, the thwack of ball meeting glove, the music over the public-address system — but no one knows for certain that these practices will even matter. As the number of confirmed cases spikes around the country, the virus may have the final say.

“Honestly, I still don’t feel comfortable,” Mike Trout, the game’s premier player, told reporters covering the Angels on Friday. “We’re risking our families, risking our lives to go out here and play for everyone.”

Trout added that he did not understand why players must be confined to their hotel rooms on the road (except to go to the ballpark), but acknowledged that one careless player could ruin everything.

“I love playing this game,” Trout said. “It’s going to come down to how safe we’re going to be.”

ImageJackie Bradley Jr., center, gathered his fellow outfielders in a socially distant huddle.Credit…Adam Glanzman/Getty Images

The Red Sox are taking no chances at their antique home. While the coaches still dress in the claustrophobic Fenway clubhouse, the players will occupy the luxury suites on the second deck, two to a room, like a college dormitory with the best view in town.

“We had an idea of what it would kind of look like, but then just seeing it in person and being in the room, it was really cool,” infielder Michael Chavis said. “And then the beautiful view of Fenway, and everything about it. I missed baseball, I missed the Red Sox, I missed the team.”

The boys are back in town now, excited but wary, together but distant.