Chelsea suffered their worst Old Trafford defeat in 15 years as United eased to a thoroughly deserved success after Nemanja Vidic had broken the deadlock in first-half stoppage time.

Wayne Rooney added another just after the hour mark before Dimitar Berbatov completed victory for Ferguson's men near the end.

United are now a single point adrift of the Londoners with two matches in hand. And if they win the first of them, against Wigan on Wednesday, they will only trail Liverpool by two and could go top with a win over Bolton next week.

Liverpool and Arsenal still have to visit Old Trafford before the end of the season, and with the first big test of their championship credentials passed, Ferguson has called on United to march on from here.

"As we've said all along we've got all the main teams at home and we really need to win those games," he told Sky Sports.

"And we've got the first one out of the road, but we've got some tough games coming up now. We've got players who are playing fantastically well at the moment on Wednesday and then Bolton away which is also a tough game.

"So there's a lot of interesting games to see in the next few weeks. January, as I've said, is a big month for us, I think we've got eight games in January so it's a big test for us."

Despite the heavy defeat Ferguson was still full of praise for Chelsea.

He said: "They had a lot of good possession at times and they're a threat when they get possession.

"They've got so many clever players, but we defended well at the 18-yard line so I don't think they really had a clear-cut chance."

Chelsea manager Luiz Felipe Scolari was not so kind about his team's performance, admitting: "Manchester United were better than us."

He also admitted that the result will have had a damaging effect on his side's title challenge.

"I think it's done some very big damage because we didn't come here to play like this," he said.

"We were thinking about winning the game. Now we need to think about the result, what happened to some players, what happened from set-plays and now we have to think about the future."

Had United not ran out such comfortable winners more may have been made of an incident from a corner just prior to United's opener.

Rooney seemed to know exactly what he was doing when he rolled the ball into, then out of the quadrant. Ryan Giggs ambled over, crossed and Cristiano Ronaldo powered home a near-post header.

Referee Howard Webb ruled the effort out and United reacted with fury, surrounding the assistant referee who had made the decision.

Chelsea were still regrouping as Giggs swung over the re-take. This time Berbatov got there first, flicking the ball on for Vidic to power home.

"I don't know if you saw the corner but we had planned that. We actually planned it," explained Ferguson.

When asked if Rooney needed to make clear to the assistant what he was planning, Ferguson said: "I don't think that, I don't think he needs to, but anyway, it's a good result."

Giggs added: "I don't think the linesman knew Wayne had taken a short one. I don't know if Wayne had told him.

"I just jogged past Wayne and he said he'd took it, so it was clearly outside the D so I just ran across and took it. But luckily we scored just after that.

"Obviously we would have been annoyed if we hadn't scored straight after it, but obviously it's good to score the goal at any time."

Giggs added that he was unconcerned about the affect such a result will have on Chelsea, preferring instead to concentrate on his own team.

He said: "I'm not really too bothered about what it does to them, but what it does to us is it gives us confidence because we'd had one point out of the previous three meetings against the top sides until now, so we've got them all at home now and we've got to make the most of it."