Manchester United boss Sir Alex Ferguson says defender Rio Ferdinand has changed his game this season.

Ferdinand has been outstanding for United since the New Year.

The United boss said of Ferdinand: "He had to change his game. He couldn't rely on his pace the way he used to as a kid because he was such a pure athlete and so mobile.

"He could outrun anyone. He used to take ­advantage of that, but he can't do that now, so his positional play is more ­important.

"He plays a bit deeper than he used to. That's not a problem ­because his experience is the vital part.

"He's taken on a lot of responsibility, with Vidic being out, and he has gone a long way in helping Jonny Evans and David de Gea.

"I think he's ­relished that ­responsibility. He's generally shown his most consistent form. Even though he was more of an athlete in his younger days, he made the odd mistake through carelessness and casualness.

"He had that trait. But now he's using all his experience and not making any mistakes at all. He's doing all the right things.

"We're looking after it, too. We don't train him every day - 'We'll have a quiet day', as we call it."