"Winfield goes back to the wall. He hits his head on the wall and it rolls off! It's rolling all the way back to second base! This is a terrible thing for the Padres!"
This is a baseball game, obviously. Winefield is a player for the Padres. He's been running to catch the ball and he's hit the boundary wall. He's hit his head on this wall, and the ball he was running to catch has rolled away, thereby
giving the other team a pretty much guaranteed home run. What makes this comment funny is the fact that the commentator forgot to mention that it was the ball that rolled off, and not winefield's head that rolled off after he hit his head on the wall.