Redknapp said: "Lassana can become top class, absolutely top, top class. We want him here as long as we can keep him, but you could see him playing in any team in the world. Watch him train, watch him play, he will go right to the top, no doubt in my mind.
"Without a doubt he is right up there with the best young players I have ever come across. I spoke to Frank Lampard about him when he was at Chelsea and he hated playing against him in training. When the chance came to sign him he was just such a good player. It was too good an opportunity not to take.
"He's an inspired player, he can do everything, he's top quality, absolute top class. People liken him to Makelele because he uses his body so well and holds people off. He's got a fantastic knack of doing that, but he has got so much in his locker really, he's more than a defensive midfielder.
"He's been in the French national team for the last 10 games. You don't play for France in midfield at the age of 22 unless you are a proper player. He can only keep going up and up and up and in the meantime take us forward to where we want to be.
"He wouldn't sign a new contract with Chelsea, he made up his mind he was going to leave because he wanted to play. He was told he would play all the time at Arsenal and I think he would have got in their team, no doubt about it, over a length of time.
"But he wants to play and I'm just glad it's for us."