If the ball is gone when you hit the QB, did you affect the throw or not affect the throw? I don't know. I do know that a sack means the QB was laid flat on his butt for a loss, and that number dropped dramatically from Jan's sophomore to junior year, but remained constant from his junior to senior year.
I also know that Jan's TFL's dropped dramatically from sophomore to junior year (a reflection of the big drop in sacks), but rose from his junior to senior year. I also know that the '09 defense was vastly improved over the '08 defense, so it would seem Jan was utilized and/or produced better as a senior than he was/did as a junior.
Jan had NFL aspirations after his sophomore year, and that's understandable. He and his supporters have tried to blame his lack of an NFL career on the slight change in how he lined up his senior year. There's just too many excuses. First it was that he was saddled with playing alongside a true freshman Manu instead of a seasoned Russel T (ironically, Jan had his best season playing alongside Manu). Then it was that he'd put on too much weight. Then it was that he was tasked with lining up shallower. The truth is that he was a tweener who had a great college season once, but that whose game didn't translate to the NFL.