Fatigue is in every sports game. 2K is meant to be SIM, so there should be no question fatigue should be in the game at any diffculties level.
In fifa it's even relative to the period lenght. If you play one halftime you're players are gona be tired the same wether it was a 5 or a 10 or a 20 minutes period. Should be like that in 2K too, I don't know why they don't do it.