Chelsea defender Gary Cahill is ready to do battle with England teammate Wayne Rooney for tonight's clash against Manchester United.

While he knows the forward's game well, he admits playing with him for England does not necessarily mean his task becomes any easier.

"It helps because you know a lot of his strengths but with certain players of that calibre you never can predict what they're going to do to change a game, you always have to be on guard," Cahill told chelseafc.com.

"He's fantastic, he likes to come off and get in the spaces to cause defenders problems. He finds pockets in between the lines which we do with our creative players, so it's going to be important we keep an eye on him."