"At 16 he had things in his game you just can't give to players," said Wenger after seeing Cesc star in Saturday's victory over Tottenham.
"Now he has matured and when it is hectic, he is the one who keeps his head. He can get you out of tight situations and play into the right space. He has vision.
"Now he can't stop scoring when before he could not. That shows the importance of what goes on in your head."