He said: "He is the best right-back in the country. He is an outstanding player. He lacks concentration at times, but when he is switched on he has got everything.
"There have been times when he has switched off and been a bit casual and has paid the price for it but he is learning."
Redknapp added: "I didn't have any problem persuading him to come here on loan and in the summer he was up for coming back. It has been a great move for him.
"We make him feel important here and he is important for us. At Chelsea, if he made a mistake he was out of the team and it is very difficult to play football when you are under that type of pressure all the time.
"Here if he knows that it will take a nightmare run of games for him not to play. I would be surprised if he was not in the next England squad."