Keller = TE version of Shonn Greene.
Talent there, about twice year has really excellent games that show he has the talent, under achieves in a lot of games over his time here. No where near as fast as what he was supposed to be. Questionable character after his near the goal line shenanigans last year.
He is no more of a match up problem than any other pass catching TE in this league. He is also apparently stupid as he turned down a multi year deal from Miami in favor of a one year deal for the same amount.