Straight from the NBA site:
Hand Checking: A defender may not place and keep his hand on an opponent unless he is in the area near the basket with his back to the basket. A defender may momentarily touch an opponent with his hand anywhere on the court as long as it does not affect the opponent’s movement (speed, quickness, balance, rhythm).
Delly played bump and run about as well as Revis, BJ (Before Joey). But, he's way too small for the NFL.