The odds were against Damon Harrison ever seeing the NFL. He was an undrafted free agent out of William Penn University. Just by playing for the Jets in an NFL game, he will be able to be proud of what he accomplished for the rest of his life.
Harrison profiles as the typical plugging nose tackle. He does not have Kenrick Ellis' athletic ability. He will probably never become a disruptive force. What he might become is a space eating type who occupies two blockers and keeps his linebackers clean.
Like Ellis, Harrison has to overcome the challenges of playing at a small school. That can be tricky. Small school projects play weak competition and were usually able to dominate using sloppy technique, which can create bad habits. Harrison will have Karl Dunbar, which is a plus.
Probably the best thing you can say about Harrison is that he impressed the coaching staff enough to get time on the field and did not look totally overwhelmed in limited work as a rookie. He still has a very long way to go to become a good player, and the odds are still very much against him ever becoming one. It could not hurt to give him an offseason and a year in camp to try and make something out of him, though.