Contingencies — a defining characteristic of our coronavirus-inflicted times. No plan can be laid with the expectation of perfect execution. None can be laid, in fact, without the possibility of a complete unraveling.

Technically, that’s always been true. But it is, shall we say, peak truth now. Exhibit A is Major League Baseball. It took four months for the league to get up and running in 2020, and just a few days for the new season to go south.

By Sunday morning, four members of the Miami Marlins’ traveling roster had tested positive for COVID-19. The team played anyway that day and won its second game of the summer — but that was the extent of the good news. By Thursday, 17 players and two coaches had tested positive. The traveling squad is now quarantined in a Philadelphia hotel. The team is on ice at least through Sunday and must resume play with a backup lineup. The Marlins’ season has two asterisks after three games.

There are also ripple effects for the league, with its already condensed schedule, and renewed talk about the value of having a season at all.

We argued previously (much has happened since) that a baseball season could be a pleasant diversion during lockdown. Now that play has begun — amid a much looser, more infected social environment — it’s been informative.

Unlike other pro sports, MLB did not strictly limit participants’ exposure to the outside world. The NBA season restarted on Thursday, but all the action is at the Walt Disney World Resort near Orlando, and players are living, practicing and playing in a bubble. The WNBA season began a week ago, under similar circumstances elsewhere in Florida, and the NHL has picked up and moved to Canada. So far, so good for those other leagues.

While MLB is not lacking in protocols, it is staging games around the country and allowing players to go home or to a hotel at night. The origin of the Marlins’ outbreak remains unknown. There have been rumors (unconfirmed) that some players went out on the town in Atlanta.

Where does the league go from here? It’s day to day. In all, three games were postponed on Friday because of positive tests. But there are lessons for the rest of us as we try to re-establish a semblance of normalcy. One: Maintain as much of a bubble around your activities as you can. Two: Don’t get too wedded to an outcome. Be ready to react.