But the Portuguese boss couldn't contain his anger at referee Martin Atkinson's decision to award the hosts a 17th minute penalty when the game was still scoreless.

Third-choice goalkeeper Hilario, only in the side because of injuries to Petr Cech and Carlo Cudicini, then denied United by saving Danny Webber's weak spot-kick.

Shortly before half-time Frank Lampard put Chelsea, who started the day level on points with leaders Manchester United, ahead when his free-kick deceived keeper Paddy Kenny and soon after the break the England midfielder's cross was headed in by Michael Ballack.

It was just the result Chelsea were looking for ahead of their Champions League match away to title-holders Barcelona on Tuesday.

But that didn't stop Mourinho venting his anger at Atkinson's decision to give the Blades a penalty for Didier Drogba's foul on Claude Davis.

"The decision for me was completely wrong," he told Sky Sports.

"The referee has made a wrong decision but after that the performance it is good to think there was one mistake, that's it. When the performance is so poor you are not so happy.

"It was a big decision against Chelsea at the beginning of the game. If Hilario doesn't save it maybe we are in trouble.

"It was not easy for us but the team fought well. We deserved the victory and could have scored more goals."

United boss Neil Warnock, one of the few Premiership managers known for being as outspoken as Mourinho, was also unhappy with the referee, particularly in the build-up to Chelsea's opener.

"Goals change games and it really would have been nice for once to put a penalty away and put a bit of pressure on them, take the lead and see how they reacted," Warnock said.

"Unfortunately it was not to be and a goalkeeping error resulted in the first goal.

"I don't understand the advantage rule. It seems to be one rule for one and one for the other.

"I'm disappointed with the result but it augurs well. I think we've got a fighting chance (of staying up)," he added after United's sixth defeat in 10 league games.