There is a way to even out minutes. Play 5 players without backups. They'll get 48 minutes, usually. But you probably mean something like getting your players 50-60 minutes a game. There is no sure way of getting those numbers because minute management is an important part of this game. The BB's have made it a challenge to get the perfect minutes every week.
In terms of randomness, I guess yes. The injuries which could limit your player's minutes are probably random. The fouls and coach substitutions probably have formulas we're never gonna be privy to ever.
Those are my best guesses.