It' pretty simple – stop the player from scoring the basket. However, it seems the Rockets forgot about this when they faced the Nuggets recently and Danilo Gallinari made the Houston defense look silly.
Off a missed shot by Houston's Chandler Parsons, Gallo snatched the rebound and was off and running. All who was left was James Harden who's defense was less-than-stellar in stopping Gallo. Pick up the foul at least Harden!
Check out Gallo going coast-to-coast on the Rockets for the big time jam.