The Grizzlies actually played the pick-and-roll pretty perfectly for the most part. Marc Gasol stayed in front of Dragic on the switch, Mike Conley defended Marcin Gortat as he was rolling to the basket, and the Suns' point guard was forced to the baseline. It looks like Gasol knew the clock was about to expire so Dragic would have to force up a shot.
He gambled that it would be a fadeaway shot from the baseline. Instead, Dragic reversed his pivot, got right in front of the basket and dropped in a hook with 0.5 seconds left to win the game. Good defense by Gasol led to a bad guessing game, and Dragic made the Grizzlies pay for it.