Moments after the Los Angeles Dodgers clinched the World Series title on Tuesday night, as their players and coaches mingled excitedly on the field before receiving their trophy, a Fox broadcaster delivered some shocking news: Justin Turner, the Dodgers’ longtime third baseman, had been taken out of the game because he had received a positive result on a coronavirus test.

It would have been a stunning revelation after any game, but this was the deciding game of the World Series, the climax of baseball’s marquee event playing out on national television in front of millions of viewers. The completion of the season had been seen as a triumph of Major League Baseball’s plan to keep the virus at bay — a plan that had been tightened during the regular season after significant outbreaks within two major league clubs.

But Turner’s positive test during Game 6 put a damper on the end-of-season celebrations and raised questions about the handling of the situation by both M.L.B. and the Dodgers, as well as about what would happen to members of the Dodgers organization in the coming days after being exposed to an infected individual.

“It’s a bittersweet night for us,” Major League Baseball Commissioner Rob Manfred said during an interview with Fox after presenting Corey Seager with the World Series Most Valuable Player Award, and before Turner was seen celebrating on the field.

“We’re glad to be done,” Manfred continued. “I do think it’s a great accomplishment for our players to get this season completed, but obviously we’re concerned when any of our players test positive. We learned during the game that Justin was positive and immediately isolated him to prevent the spread.”

Turner, 35, who has been with the Dodgers since 2014, was replaced before the start of the eighth inning of the 3-1 win over the Tampa Bay Rays. At the beginning of the Dodgers’ postgame celebration at Globe Life Field in Arlington, Texas, Turner was not seen with his teammates on the field. He posted a tweet shortly after the game saying he had no symptoms, adding: “Can’t believe I couldn’t be out there to celebrate with my guys!”

But minutes later, Turner was back on the field: holding the trophy, kissing his wife and mingling with other players, coaches, team officials and family members. At times, he was wearing a mask. During other moments, including the team’s group photo with the trophy, he was not.

The Fox broadcast showed him removing his mask while sitting between Manager Dave Roberts and Andrew Friedman, the team’s president of baseball operations, for the group photo.

On a video call with reporters later, Friedman denied not wearing a face covering himself — though the broadcast showed him posing with the rest of the team without a mask. Asked again later about the message the Dodgers sent by not wearing masks, Friedman said, “If there are people around him without masks, that’s not good optics at all.”

Friedman said Turner, a team leader whose strong play helped the Dodgers win their first title since 1988, wanted a picture with the trophy. “For him, just being a free agent, not knowing exactly how the future is going to play out, I don’t think there was anyone that was going to stop him,” Friedman said.

Friedman was later asked to clarify if the decision to return to the field was solely up to Turner. “It wasn’t up to Justin,” he said. “I think Justin wanted to come out and take a picture of the trophy, and did.”

The Dodgers’ star outfielder Mookie Betts, speaking to reporters on a video call, dismissed concerns about Turner being on the field. “Forget all that,” Betts said. “He’s part of the team. We’re not excluding him from anything.”

Although Friedman admitted he hadn’t watched Turner closely given the commotion of the celebration, he said Turner — who did not speak to reporters after the game — had been mindful of others, especially those he “hadn’t already been in contact with.”

“From our standpoint,” Friedman added later, “I think the people who were around him were people that would be in the contact tracing web anyway, with just how closely a lot of us have been around each other. So now the subsequent tests we’re going to take are really important to figure out what we’re doing to make sure that any of us that are potentially positive do not spread it to other people.”

Friedman said he was unsure when the Dodgers would be able to return home to Los Angeles, but for now they planned to return to their hotel to undergo testing and contact tracing.

“Congratulations to the LA Dodgers on winning the World Series,” the MLB players’ association said in a statement on Twitter. “We’re obviously concerned with respect to the report of a positive test and we will work with players, their families and the league to see that all precautionary health and safety protocols are followed.”

Friedman said that the Dodgers had learned of Turner’s positive test during the seventh inning, a moment he described as “extremely surreal.” Word was sent to a team trainer, who told Roberts that Turner needed to come out of the game immediately. Turner, who went 0 for 3, was replaced by Edwin Rios at third base at the beginning of the eighth inning, when the Dodgers were leading by 2-1.

Seager, a shortstop who has played alongside Turner for six years, said it was “gut-wrenching” not to have Turner on the field for the end of the game and immediately afterward. He said he wished he could have switched places with Turner.

During the regular season, players and on-field staff members were tested for the virus every other day. But during the postseason, the testing was increased to every day. As of Friday, M.L.B. reported that there had not been a positive virus test among players for 54 consecutive days.

For the final three rounds of the postseason, which were held at neutral sites to cut down on travel and potential exposure to the virus, the Rays and Dodgers, like other teams in the playoffs, were in so-called bubbles: They were restricted to hotels that were closed to the public and taken to and from the stadium. Players’ wives and children were allowed to join them as long as they had quarantined.

After larger outbreaks temporarily halted the seasons of the Miami Marlins and St. Louis Cardinals early in the truncated 60-game regular season, M.L.B. became more aggressive about postponing games when positive cases arose. The league also tightened their coronavirus health and safety protocols, including adding compliance officers to monitor clubhouses and team hotels.

Players and coaches were required to wear face coverings everywhere at the ballpark, including in the dugout and in the bullpen. (One exception: players on the field.) Over the course of the year, that rule was sometimes ignored, including on Tuesday.