That was a designed defensive play. G Williams had noticed that when Manning read a blitz from his right he would check out to a quick slant to Reggie Wayne on the left. Williams called for that blitz early in the game to test his theory but instructed Porter to lay back. Manning completed the pass for a 5-6 yard gain. That was a setup for later. When Williams saw the right time to call it again in the 4th Quarter he did but this time Porter had the signal to jump the route and one of the greatest plays in Saints history happened.