Oh yeah, he is "average." He is the fastest Bufalo Bill RB to reach 2,000 yards in his career (faster than OJ, Thurman, Joe Cribbs et al). He also is playing behind one of the worst lines in Buffalo Bills history. He also has done it without getting that many carries.
Go ahead. Keep on saying he is average. If you say it enough times, you may even begin to believe it yourself.