Manchester United boss Sir Alex Ferguson explained his early substitution of Wayne Rooney during their victory over Portsmouth.

Rooney has now scored seven goals in four games after sending a header beyond David James and was presented with the Barclays Premier League Player of the Month award before kick-off.

With Aston Villa next up on Wednesday, Ferguson said: "He is in great form.

"It was a great opportunity for us to give him a rest. We had fresh players to come on like Mame Diouf and Michael Owen."