MLB has postponed Friday's game between the Cardinals and Brewers in Milwaukee after two members of St Louis' organisation tested positive for coronavirus.
The contest at Miller Park in Milwaukee will now take place on Sunday as part of a double-header, with MLB explaining that would allow sufficient time for additional testing and contact tracing.
It means six of the 30 MLB teams will now not be playing on Friday as a result of postponements caused by positive COVID-19 tests.
The Miami Marlins, Washington Nationals, Toronto Blue Jays and Philadelphia Phillies are the other clubs affected by outbreaks.
In a statement, Brewers general manager David Stearns said: "We are supportive of Major League Baseball's decision to postpone today's game and look forward to playing our home opener as soon as conditions safely allow.
"The health and safety of our players and employees are, and will continue to be, our top priorities."
The Cardinals issued a statement disclosing the positive tests emerged late on Thursday.
It said players and staff have been told to self-isolate in their Milwaukee hotel rooms "until further notice".
"The team is currently conducting rapid testing of the entire travelling party, has implemented contact tracing, and will continue to self-isolate," the Cardinals said.