As our fearless leader continues to point out, quarantines/masks/lockdowns/etc. are the same thing as CDC "guidances" - they're not LAWS (unless they benefit him in some way). For instance, the Governor here in NC has mandated that everyone wear masks in public, but our local Sheriff openly pandered to the backwoods redneck/Trumpites in a Facebook post unequivocally stating that our County would not be participating in enforcement of that mandate.
I would assume that visiting players and personnel would be quarantined to their own hotel and the ballpark when they fly in - they won't be allowed to sightsee, patronize local restaurants or bars, etc. while they're in town. I'm assuming the same thing goes for NASCAR and the PGA Tour players since they're back at work in multiple states.