I am assuming some injuries. But even without that possibility, you've got the following players trying to make the Opening Day roster (including the three-man squad) who aren't on the 40:
Walker/Forsythe/Harrison (probably just one of them)
Torreyes, Gosselin (former can play SS, latter can play CF, neither is an actual need, but it's not out of the question, managers love having that glove-first guy even though our 3B and 2B can both play SS too)
Liriano (he seems to have already "won" the minor league free agent reliever derby but we need to know if he has an opt-out or not)
Kelley, Parker, McClain
And then Bohm and Howard, whether it's on Opening Day or at the end of July.
I'm assuming Williams, Garlick and Gamboa's spot on the 40-man is shaky (unless Garlick makes the 30-man or Bruce gets hurt). Ditto Austin Davis. Seranthony will go on the 45-man. Lots of other fungible relievers still on the roster but the plan there is probably to see what they have (or use them up) before changing things.
Sanchez another guy on the 40 who's not on the 60. Also, we may need to replace Wheeler for a while though we still don't know how the "COVID IL," or taking a leave of absence for Covid-related reasons, affects the rosters.