Nationals general manager Mike Rizzo said in a videoconference with reporters that his team also has a fourth player considered a "likely positive." He did not identify any of the players involved.
"For the most part, the whole team has been -- we put them -- in lockdown and they're self-quarantining," Rizzo said.
He said it was not known when the season-opening game will be made up -- other than that it would not be played Friday, originally set up as a day off to allow for a makeup contest if there were an issue with Game 1, such as a rainout.The next game scheduled between the two teams is Saturday at 4:05 p.m. ET.
"It's a shame that we can't play today, but we need to stay positive. I've talked to a lot of players and my concern is about their health and safety," Washington manager Dave Martinez said. "I'll continue to reach out to them to make sure they're OK. We're going to get through this.
"This isn't the first time we've been through some bumpy roads. We've been there and we're going to come back from this and we're going to play baseball."
Rizzo said one of the players testing positive had a fever, while the others were not displaying COVID-19 symptoms.
On Wednesday, Rizzo announced an initial positive test for the illness caused by the coronavirus. He said it resulted from testing done Monday, while the Nationals were still in Florida for spring training.
At the time, he said four other players were considered to have been in close contact and were quarantining. Now, two of those players have had positive tests after being tested Wednesday and another had an inconclusive sample that is being treated as a likely positive.
Contact tracing was continuing, Rizzo said, to see who else might have been exposed.
The Mets worked out at Nationals Park on Thursday, with pitchers throwing live to hitters.
"It's unfortunate. There are things that are still happening in the world. To be honest, it wasn't a surprise. We've been in situations like this since last year," Mets manager Luis Rojas said. "The health is the No. 1 thing still in the world. We're taking care of ourselves. Everyone's taking their mask everywhere. We're doing everything we need to do."
Rizzo said he was not sure how the team outbreak began.
"I've got the utmost confidence that it was not a player breaking protocol. We were very diligent throughout the whole spring training. The day we landed in D.C. was the day we got our first positive," he said. "It's only conjecture on what happened and when it happened, and we don't want to get into that. This is a serious business. It's about people's health and these players, obviously, they're very important to me and to our organization."
The team flight from Florida to Washington after the end of spring training was where there was close contact among players and staff.
Max Scherzer, who had been scheduled to pitch for the Nationals on Thursday night, said he was not on that team flight and traveled separately with his family.
The Nationals did not have a single player test positive during their six weeks of spring training camp in West Palm Beach, Florida, according to Rizzo.
He said the team would follow both Major League Baseball and D.C. protocols regarding quarantining.
Per MLB's health and safety protocols for 2021, any player who has tested positive will be required to isolate for a minimum of 10 days, receive appropriate care and monitoring from the club medical staff, and be cleared by baseball's joint COVID-19 committee and the individual's team physician after a mandatory cardiac evaluation and a determination that the individual no longer presents a risk of infection to others.
ESPN's Jesse Rogers and The Associated Press contributed to this report.
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