Note it says in most cases it will lead to a tear of the hip labrum which is what happened to Mesoraco. It's pretty easy to see, how the axial and torsional force put upon the hip joint would lead to problems for catchers and pitchers.
Here is an article on pitcher Josh Beckett that does a pretty nice job of explaining the three types of impingement deformities that can occur (Cam, Pincer, or combined):
http://www.beyondtheboxscore.com/201...ngement-injury
Remember, Mikesell was a pitcher and a very good one at that coming up through high school. This injury could have been something that stems from that which wasn't properly dealt with. Fortunately, coming back to basketball seems like it might be easier though than coming back from the injury as a pitcher.
Here is an article that details hip injuries in NBA players. It does a pretty good job of explaining the injury and detailing the prevalence of these injuries, but unfortunately does not give information in the way of recovery times:
http://instreetclothes.com/2015/11/1...es-in-the-nba/
But I would be very surprised to Mikesell rush back because of having that medical redshirt year available. Totally different situation than Josh Cunningham's, where Mikesell will be guaranteed eligibility as a 5th year senior if he misses this year, where Cunningham faced an iffy proposition of getting the NCAA to grant a 6th year.