Heres what we know so far. 3,185 players were tested last week and the confirmed infection rate came back at a relatively respectable 1.2% from that sample. Much better than the NBA and much better than the general population.
But the plan is play in home stadiums which means travel to and from states such as Florida, Texas, Arizona and California who host 10 of the 30 teams in 4 of the 6 divisions and 2 of the three regions (central excluded for now).
There will be rigorous testing and contact tracing in order to limit the spread, but no real quarantine for the players at home or on the road (if I have missed guidelines on this please let me know, though even with guidelines it would be impossible to police).
There will probably be a degree of peer pressure from within rosters to encourage the sort of behaviours that would limit infection and spread especially in rosters where there are players who have been infected with real symptoms, or have familly members who have been hit hard, or who have family members who are high risk but really it only takes one careless player to infect a significant portion of the rest of the team.
On one hand there are obvious financial incentives to not getting infected and not infecting your team mates. If the league gets cancelled then the players won't be paid. Also, no one wants to be Rudy Gobert even if his actions ended up saving lives in the long run by getting the NBA and other leagues postponed and waking people up to the fact the virus was very much spreading in the US.
On the other hand, the league as a whole skews further to the right than say the NBA and we've seen how this issue has been politicized and how wearing a mask or not is almost a statement for some rather than a measure to slow the spread. You also have to deal with the fact that for players on minimum salaries the financial incentives in 2020 are not all that great. Pro Rata they will only earn $208,704 and some of this has already been advanced so for some players they may only be talking about an additional $100k in real terms for 60 games.
Its easy to say they will earn that $100k if they can stay semi quarantined for just 66 days from opening day but lets imagine a player who fits this profile - young prospect, probably had their service time manipulated at some point, has enough money in the bank from their signing fee so that 100-200k isn't that big of a deal and they expect to make tens of millions over the next half decade anyway. Young and healthy, so feels invincible, not that worried about catching it and even if they do they won't be badly affected, and anyway its probably a hoax, or blown out of proportion to hurt Trumps chance of winning in November. First time on the road in Miami or LA or some other great party city, and they have enough money to have a great night on the town, and bars and clubs are open so why not have a good time, you only live once.
There might not be a player who fits this description on every roster, but I bet there are a few scattered throughout the league who fit this or something close to it, even if you take out the political stance.
So maybe the league gets started but if we have one or two teams who have a cluster of infections, say 10 or 15, what does MLB do? If its Baltimore or Detroit, or Miami, maybe they play on without them and give their remaining opponents an average win rate against them and if a wild card spot ends up being decided by that then they play a one game play in. What if its the Yankees, or Braves or Dodgers or Astros?