I'm in a league with only 2 preseason games and I hate it, way too short. I like having 4 preseason games as the opponents playing style will vary more, giving a better read on new players.
Imagine if we only have 2 preseason games and somebody has both Detroit and Tampa on their schedule, or any 2 top tier teams. That team's players will not likely fare very well, and you're left wondering...do they **** because of the competition or do they just ****?
There are ways around injuries, if you play with the depth chart you should be able to find someone to cover a position of need in a meaningless game, even if it's a 225 lb DE or 276 lb MLB. If you can't or won't do that, one thing I do is sign some old guy to a 1 year minimum contract, or any guy you know you will cut.
Once that player is cut, it only counts like $15,000 against the cap. Just make sure you doubt you'll ever want to resign him because doing this often makes them unwilling to sign with you in the future.