Redknapp wrote in The Sun: "I listen to the experts who write him off as past his best - and it's nonsense. He has 81 caps so far and, while it might be a tough task, he has it in him to reach 100.
"I understand the decisions Rio has to make but I sincerely hope he carries on playing for his country for as long as he can.
"Just a couple of weeks ago I watched Rio in action for Manchester United at Queens Park Rangers. He was outstanding. I can't think of another English centre-half who would beat him for pace over any distance.
"Rio could have been a midfielder as well as a defender. He was - and still is - so comfortable on the ball that he seems blessed. And what do you want from your squad at a major tournament?"