I can't blame his choice of leaving ND early. This was probably the best choice for him, since as a 2nd or 3rd rounder, most rookie contracts are 4 years or less, as opposed to the longer term deals for 1st rounders.
Hip labrum tears that require surgery can take up to 9 months for ordinary people to regain full strength.
For athletes, especially those with realistic NFL aspirations, it could take even longer before they get back to their peaks, since they'll have to undoubtedly undergo significant PT to get the muscles back in shape.
Had he come back, the odds are more than good that he would miss part of the season season, and that would push him even further down the ranks.