he thought the ball was going to get lose on the infield. Pirtle was slowing down at 3rd, and then suddenly took off without ever picking up the ball.
There may be blame to share but I put more on Mingione, I didn't see any hand signals from him at all either way on the replay. Pirtles' back is to the rightfielder, he's got to be getting some input from Mingione before he hits the 3rd base bag and you can't rely on verbals.