Redknapp said: “He has got stronger, he's grown up and is tougher. He's mentally tougher.
“I always felt he would get a little knock and limp off in training. He doesn't do that any more.
“Maybe it's because I said to the physio 'when he gets injured leave him on the floor. Don't keep running over to him'.
“The defensive part of his game has improved. He realised he had to improve that. We talked to him about it and worked with him in training. Now defensively he's not vulnerable.
“He's a different boy altogether. He's aggressive, strong and has everything to be a great player and is now showing the ability I saw when he was a kid at Southampton.
“There can't be a better left-sided player anywhere. If he were English he'd be going to the World Cup now, that's for sure.
“He can play left-back or wide left in midfield, he's six foot and has great a physique. He can run all day, has an unbelievable left foot, has skill and his heading is top-class - he can do everything.”