Wenger did all he could to keep him but couldn't.
He is so quick and mobile, reads the situations well and is also a good header of the ball.
I think he benefits Joleon too with his extra pace and the fact they cover each other well.
He is very hard to beat and with his pace he's like a left winger. Going about his job very well. Also Kolarov is a good player too, but Clichy is a better defender.