Manchester City defender Kolo Toure has warned title rivals Manchester United their defeat to Wolves could signal the start of a dip in form.
United were beaten 2-1 at Molineux on Saturday, a result that ended their hopes of going through the entire Premier League season unbeaten.
Toure, whose City side go to Old Trafford this weekend, was part of the Arsenal side that went through the 2003/04 campaign without tasting defeat.
And he believes that United now face a stern examination of their credentials after recalling how Arsenal struggled when their run eventually ended with a defeat to Sir Alex Ferguson's men.
He said: "When you're on a good run like that and you lose, everything becomes harder. It shakes your confidence. Maybe that can happen to them. It was difficult to lose that game.
"The circumstances were hard because they got a penalty, which we didn't think was a penalty. For us, it was really difficult to lose to United. I think it's a great chance for me to get my revenge.
"I have spent most of my career in England battling United, first at Arsenal, now at City. They are always at the top. Now we have new players, we are capable of fighting against them and that has been shown with our results against them over the last 18 months."
