Michael Vick's Second Chance

For a time, Michael Vick was one of the most exciting quarterbacks to watch in the National Football League. Many thought he would redefine the position. Of course, since then his moral and legal troubles have been widely reported on and discussed ad nauseam. Vick has now been reinstated in the NFL on a conditional basis, with full reinstatement a possibility. Professional athletes commit all sorts of crimes, and are allowed to play. I'm interested in what people think about Vick and any other athlete who is convicted of a serious (i.e. harmful to other sentient beings) felony. It seems that the current commissioner of the NFL has a policy of being more strict, so to speak, about these sorts of cases, though he has conditionally reinstated Vick. Why might the NFL be justified in not reinstating Vick, or athletes convicted of assault, spousal abuse, and so on?