Manchester United striker Wayne Rooney says they're not worried about the new cash power of derby rivals Manchester City.

"It is down to them what they do with their money," said the England striker.

"But we know we are the best team in the world are at the minute. It is there for them to see.

"Sunday is just one game of football and you cannot read too much into it.

"But it still hurts that they did the double over us last season, so we will be looking to do the same to them, having won at Eastlands."