8. Kendrell Bell
Bell set himself incredibly high standards in his rookie year but was unable to keep his momentum rolling into his sophomore season. In short, he suffered an unfortunate slump but you could argue that he peaked too early. The Defensive Rookie of the Year award winner made the Pro Bowl as a rookie.

Typically defensive players grow into their roles in the NFL while the likes of running backs and quarterbacks show signs of regression. However, Bell is an outlier on this list. He achieved nine sacks in his first season with the Steelers but it took him three more seasons to match that output.