On Monday, Major League Baseball officially postponed this week's four-game series between the Cardinals and the Detroit Tigers because of St. Louis' ongoing COVID-19 outbreak. Thirteen individuals with the Cardinals' traveling party have tested positive dating back to last week, including seven players. The Cardinals' weekend series against the Milwaukee Brewers was originally postponed after a pair of players tested positive.
Cardinals executive John Mozeliak addressed reporters about the situation on Monday. During the course of his press conference, Mozeliak was asked to comment on a rumor that a few Cardinals players had recently passed time at a Minnesota casino. That rumor seemed to originate from former big-league veteran Jerry Hairston Jr.'s Twitter feed, and was later corroborated by MLB Network's Jon Heyman.
"I have no factual reason to believe that is true, and I have not seen any proof of that," Mozeliak said, according to ESPN's Jeff Passan. "If they were at a casino, though, that would be disappointing."
Mozeliak later said that based on the contact tracing that had been conducted, he was "confident the outbreak originated in St. Louis," per The Athletic's Mark Saxon. Assuming the tracing was done correctly, and that Mozeliak's conclusion is right, that would eliminate the Minnesota casino as the origins of the infection. (It's possible, of course, that players who later tested positive went to the casino and, instead of contracting it there, potentially spread it.)
Wherever the Cardinals players became infected, MLB is trying to clamp down on the possibility of further spreads. Heyman noted that MLB has since "tightened its rule on leaving the team hotel from very strongly discouraged to not allowed."
What, exactly, the league is doing to prevent players from leaving the hotel is unclear at this point. More clear is that the league's policies have not prevented a pair of teams from suffering outbreaks less than two weeks into the season.