Every season has roster attrition in college football. This goes beyond the usual graduations or early NFL departures. Guys transfer. Guys simply leave school. Guys just stop playing football due to injuries. It happens. When I last looked at Purdue's football scholarship grid I had them 5 scholarships over the 85 limit once the incoming freshmen get here in the fall. After going through the spring roster I was able to find a few players that have quietly left the program before next season:
J.J. Prince - Prince was in line to be a fifth year senior, but he is no longer on the roster after starting nine games in 2014 at offensive guard. He was banged up last season after offseason shoulder surgery on both shoulders and ended up not playing much, if at all. Prince already has his degree, as he graduated in five semesters, so he may have just shut it down or transferred elsewhere to play immediately. Purdue could use him given the depth issues up front.
Joey Warburg - Warburg is a little used offensive lineman from Louisville that would have been a fifth-year senior. He wasn't even on the two deeps last year.
John Strauser - Strauser was slated to be a 4th-year junior and potential contributor on the defensive line. He played in all 12 games in 2014 as a member of the punt team and also played there extensively in 2015. He never played on defense, to my knowledge.
Matt Burke - A tight end from Florida, Burke was also slated to be a 4th-year junior but had not played at all from anything I can find.
Trae Hart - in 2014 it looked like Hart was on to something. He played in all 12 games as a redshirt freshman and even started four. He finished with 9 receptions for 80 yards. Last year he played in seven games and grabbed 7 receptions for 31 yards. He had also served as a punt returner in his career, but he is now gone. After having over 2,000 yards receiving during his junior year in HS you have to wonder if he was wasted talent.