Sir Alex Ferguson blamed referee Martin Atkinson for Manchester United's 2-1 loss away to Chelsea on Tuesday.English Premier League leaders United took a 1-0 lead through Wayne Rooney in the 29th minute at Stamford Bridge.But David Luiz equalised for Chelsea on 54th minutes.The defender was lucky to not receive a second yellow card from Atkinson after tripping Rooney midway through the second half.Chelsea then benefited from a contentious penalty decision to win the match through Frank Lampard's spot-kick with 11 minutes to go."The penalty kick was so soft," Ferguson said."Deary me. But we played very well. It was a great performance by us. We didn't deserve that.""That's three years in a row (at Stamford Bridge) referees' decisions have changed the game."Ferguson struggled to comprehend how Atkinson failed to spot Luiz's foul on Rooney. "It was incredible," he said."Even before that he'd done Chicharito (Javier Hernandez) off the ball. He'd done him late. Nothing done, the referee's in front of it.""He does Rooney clear as day, (the referee is) six yards from it, he doesn't do anything. That changed the game.""These are decisions that change the game. And he's going to be refereeing every week.""But I'm proud of the players. They've endured a lot of decisions against them but they've come through it, they've done their best. They've created good chances.""They didn't deserve that."Even Chelsea boss Carlo Ancelotti admitted that Luiz may have been lucky to escape without punishment. "There was a lot of intensity and it was not easy for the referee to decide every time," Ancelotti said."David Luiz could be lucky but there was a lot going on on the pitch so the referee decided he didn't see this.""We kept going with strength, intensity and power in our performance.""It was really good but if you don't play well, you cannot beat Man United.""It was a good performance and we are still alive."