Best comparison is who has he out accelerated and/or out ran during a game. If he's running toe to toe with DB's then I think he is fast enough. I 've seen him out accelerate LB's with Ease, and it seems corners are similar in speed to him.
I think we will see an improved Willis this year, with the new offense. Our offense will "open it up" a little in the passing game, and the runs will be disguised unlike in previous yrs with Mularkey. I had no coaching experience, yet I could forecast 90% of the plays based on the formation w/Mularkey. I always wondered, why doesn't mularkey run out of a passing formation, or pass out of a running formation once and awhile to keep the Defenses honest. I think with our current team, we will be playing for something down the stretch.