The defender has, however, been back to his best this season and Sir Alex believes close management of his fitness regime and the games he plays will see him carry on playing for a while yet.
“It [Rio’s form] has not surprised me in the sense that he’s still young for a centre-back. In normal terms you would expect a centre-back with his athleticism to play well into their thirties anyway,” explained the boss.
“He’s had the back problem which we all know about so we’ve had to manage that and by managing it properly he has adapted really well to it.
“If you look at the week before last for instance - I didn’t want to play him in Bilbao, but with [Phil] Jones calling off with the flu, I had to and then he played on the Sunday as well [at Wolves]. So he’s adapting really well to the challenge of making sure he is fit and fresh to play in the games we need him.
“What he is doing at the moment [in terms of fitness] is good. He has no issues at all. I think from time to time he gets the odd tweak in his back but we’ll manage that and look after it.”