Rob Manfred contends the MLB's health protocols are working despite outbreaks of COVID-19 on multiple teams.

"I think the vast majority of our players have done a really good job adhering to what are difficult protocols," Manfred said. "They're contrary to the way people normally live their lives.

"Relatively small deviations from the protocols can cause serious problems. That's a reality. ... Any individual act, you say, 'Wow, not a big deal,' but those individual acts can cause problems."

Manfred believes the outbreaks of the Marlins and Cardinals can be traced back to lapses in the protocols. 

"We believe, in the two serious outbreaks, that we can identify deviations from the protocols that resulted in the situations that we had," Manfred stated. "The key is vigilance. It's vigilance on the part of the commissioner's office, club officials, players and everyone involved in the game."

The MLB plans to reduce rosters from 30 players to 28 starting on Thursday for the remainder of the regular season and playoffs.

The initial plan had been to reduce rosters to 28 this week before reducing them to 26 after another two weeks, but the outbreaks of COVID-19 have forced MLB to change plans.

Theo Epstein was asked about roster sizes and said his team would support "anything that will help players stay safe, help players and staff get through the season healthy, both in terms of COVID-19 and staying safe on the field."

"As long as a rule adjustment is conceived to keep players safe and can be applied fairly across the board, we'll be supportive of it," Epstein said.