If it was a disciplinary or academic issue he wouldn't be on the sidelines so from what I gather it is either an injury or an illness. The way the medical redshirt works is if a player plays only 10% of the total games due to an injury or an illness then the team could ask the NCAA to give the player the extra year
Hammer another item for you I understand that former AD Jim Fiore has a son starting as a RB on Ward Melville's JV