He said: "I watched his league debut against Wigan and I think he showed everyone what he's about as a player.
"I don't have much doubt he'll become one of the best players in the league here, especially if he continues to play like he did on Sunday.
"If he helps Chelsea win something, he can become the best player in the Premier League.
"He's a quality player, really special - he is relaxed with the ball. Every time, just before he gets the ball, he knows what he is going to do with that. He is so quick.
"He did against Wigan what he did for Lille on many, many occasions.
"I spoke to Eden before he joined Chelsea. He asked me about the Premier League and I told him 'It's the best league in the world' and that if he wanted to truly progress as a footballer, he had to join us over here.
"He had a choice and for me, Chelsea are a great option. The best way for him to improve again and become one of the big, big players in the world - which he can be - was to move here.
"He is my friend, so I will smile with him. I've played against him once before, when France played Belgium, and we drew 0-0 and I'll look forward to this."