Manchester United manager Sir Alex Ferguson admits Chelsea have a 'major chance' of claiming the Premier League title this season after his side's defeat at Arsenal.
The Gunners edged past the Red Devils thanks to a 56th minute strike from Aaron Ramsey, although there were two controversial moments during the game.
Nemanja Vidic handled the ball in the box to deny Robin van Persie a head on goal from close range in the first half, but referee Chris Foy gave nothing, and he again failed to blow late on when Gael Clichy appeared to foul Michael Owen just inside the area.
Chelsea go to Old Trafford next weekend and Ferguson admits it is now make or break for the Red Devils and the Blues.
He told Sky Sports: "Obviously, it gives Chelsea a major chance now and that's what happens when you get these decisions.
"They got one at Old Trafford last season so that's the worry now.
"But in terms of ability - a game at Old Trafford, the supporters will be ready for it - and so will our players."
Ferguson believes United dominated the clash at the Emirates Stadium after Wales international Ramsey had opened the scoring.
"After that we dominated and I think we deserved something," he added.
"I think we didn't use the ball properly but once we lost the goal we were in their half most of the time."
Meanwhile, the wily Scot was left disappointed with the decisions during the game, conceding that Vidic should have been penalised for handball.
Ferguson bemoaned the failure of referee Foy to give his side a penalty when Owen went down in the closing stages.
He remarked: "It's too big a game not to get the decisions right.
"It balances out but I think it was difficult to see that one (Vidic's handball) but the one at the end, Clichy knew, he put his hands up in horror."
Who will win the Barclays Premier League?