This game was going very badly for Niemi. Within the first 2 minutes, the score was 0-2, favoring the Penguins. It was pretty bleak from where I sat. McLellen pulled Niemi and put Greiss in net, who played the remainder of the game.
Drew and Randy (Sharks commentators) mentioned that this was likely a message to Niemi that he had to be better and also to the Sharks, who had to do a better job of supporting their goalie.
Props to Clowe for firing up the team with a solid fight (Winchester, also.)