http://www.athleticscholarships.net/2012/07/17/how-get-medical-redshirt.htm
Medical Hardship Requirements
To be eligible for a medical hardship waiver, a student-athlete has to meet the following criteria:
The student-athlete must suffer the injury during one of their four seasons of college competition or during the senior year of high school.
The injury must be incapacitating. That means it must be a season-ending injury.
The injury must occur prior to the start of the second half of the season.
The student-athlete must not have competed in more than 30% of the season or three contests, whichever is greater.
According to this site, it just says that the injury must happen before the second half of the season, which it did. Since it is the same injury he is dealing with, he may still be eligible for a redshirt since he is still under the 30% of games played for the season. I may be wrong though.
Edit: Looking at the one above it. I guess since he came back for a game that disqualifies it from being season ending since he played a game. These rules are so hard to actually understand.