The Cameroon international paid tribute to his 64-year-old boss, who missed Thursday night's Europa League defeat to Rubin Kazan after undergoing a procedure to widen narrowed arteries.
Speaking to the London Evening Standard, Assou-Ekotto said: "After what has happened this week, I think it is important that we wish the gaffer a full and quick recovery.
"When I heard he was in hospital to have minor surgery on his heart, I was really surprised.
"There are many good football managers but very few exceptional ones. Harry Redknapp is one of those exceptional managers.
"Harry's style is very relaxed, so sometimes you can forget the stress he has to deal with but that is probably because he hides it so well.
"He is very laid-back in the way that he works with us, which is why I think he is a cool man."