Wisconsin officials say he has unofficially run the 40 yard dash in the low 4.4 second range, a time that many defensive backs would envy. He is a solid open field tackler, and has the speed to run down backs and receivers from behind. Casillas is at his best in coverage, where his speed and instincts allow him to make plays. He can cover tight ends and running backs with ease, and is excellent in zone coverage. He has a knack for forcing receivers to run their routes into the deep safeties in cover 2, taking away a quarterback's options. If he is as fast as reported, he might even be able to convert to strong safety in the NFL.