He ran a good forty time (4.57), but consider that he did it in a 6'1", 240 pound body. That's 4-3 linebacker size. He also has short arms. He's basically a faster Nick Reed. Irvin and Mingo are also around that weight, but Irvin is 6'3" and Mingo is 6'5". They could add weight and get up to 250 or 260 if they wanted without losing much speed. Not sure that's true for Williams. I'd stay away. Williams came from the Big East too, which is basically the WAC East.
His tape is pretty "meh", too. If he was special, I'd think twice.
I wonder if Seattle might draft him to take a look at LB? He might be faster than most available LBs in the late rounds.