The Miami Marlins, who had four players who had tested positive for COVID-19 as of yesterday, have had an additional eight players and two coaches test positive, per Jeff Passan on Twitter. The Marlins are remaining in Philadelphia, where they played this weekend, for the time being, and their home opener tonight against the Baltimore Orioles has been canceled.
This is a scenario that I think was anticipated as being a possibility in sort of an abstract way when starting up the season was discussed, but having it occur at the very beginning of the season is quite sobering, and is, quite reasonably, going to raise questions about the feasibility of trying to play in the midst of the pandemic.