I've been giving Superstar difficulty a shot in the demo and in a game today I had Andrew Bynum get shaken up on a collision in the paint. There was no foul but I saw him holding his back and he was somewhat out of the play as I ran back on defense. It was acknowledged in the commentary, as was his ability to remain in the game as I didn't try subbing him out and the game didn't force me to do so, so I'm guessing it really did register as a minor injury and wasn't just a phrase randomly thrown out on the collision. Presumably if I was playing a Dynasty game, there'd be a chance he'd be day-to-day or unavailable following an "evaluation" after the game.
I also presume that there will also be severe injuries that will force a timeout and substitution, though if it happens again I'll try subbing out the player and see what happens in that scenario. That's a definite improvement if injuries don't have to depend on shooting fouls in NBA Live 10 though as that obviously isn't always the case. Having the players clutch a body part and fall out of step with the play is quite realistic as well.