Wenger said: "He pops up when you need it. He is a leader and that is the best definition of a leader. When you need it he shows the example. He did that against Manchester United in the last seconds. It shows he is a winner.
"I'm not sure I would have jumped behind Cech because I think I would have thought he would have taken the ball.
"Arsenal is a special club. William this season has taken that on board and he is completely the leader and represents how we want to behave.
"He is transformed completely, does a lot of things with the team but also off the pitch which are great for the club."