Name 1 player that has gotten better during his career

I posted this question another thread, but thought it deserved its own.

Can anyone name a single player that has improved his technique, production, or consistency during his career under Sumlin?

We have scads of talent, and lots of impressive debuts, but seasons and careers seem to consistently regress. How else can we consistently have "young" teams of underclassmen, but they don't become upperclassmen leaders? Garrett is close, but even his impact is not what it was. Injuries and double teams at least explain his situation, though.