Man, that's terrible news. Sucks for Tua and his family.
For those blaming Saban, Tua played just fine earlier in that game, this wasn't a foreseeable (re)injury or a case where he was out there in the 4th quarter of a game that's already in hand. This is simply a freak situation that could not have been foreseen or reasonably prevented. This "he shouldn't have played at all" stuff is BS. If the kid is good to go and says "get me in there coach, I'm fine", and the medical staff says he's fine to play, then obviously he's going to play..... and then in the 3rd quarter when the game is in hand he goes to the bench.
Just very very unfortunate, and I hope that he recovers fully and that if not there's a hefty insurance policy he can fall back on.