"It was a really good performance - a performance of maturity," said Ferguson.
"We've seen a team mature over the last six months and today they hit their high peak."
That will serve as a warning to Chelsea and Arsenal, although striker Didier Drogba, who scored both goals against Arsenal, is confident the Blues can spring a surprise.
"I think the win gave our club the belief we are still in the race against United," said the Ivory Coast forward.
"Arsenal are not out of it yet but I'm not sure what this defeat has done for their confidence.
"I hope we can go on and win the title. The way we celebrated today showed how much the league means to the team."
Drogba's performance pleased Grant, who is adamant his top marksman is back to his best.
We will fight until the end and we are not worried about the future
Arsenal boss Arsene Wenger
"Didier was not so good when he came back from the African Nations Cup but last week against Spurs he was better, and today he was very good," said the Israeli, who saw his side fall behind to a Bacary Sagna goal.
Manager Arsene Wenger refused to rule out his Arsenal side's chances in the title race despite this latest blow which means that the Gunners have not picked up a win in six league games.
"We will fight until the end and we are not worried about the future but are disappointed now, obviously," said the Frenchman.
"Today we were unlucky and I thought we played well. We were 1-0 up and were unlucky with their first goal, which I thought was really offside.
"Nicolas Anelka came on for them and they decided to play long-ball, which put us under a lot of pressure, and that was the only way they could trouble us.
"In the end we lost the game. It is disappointing because we gave everything but now the priority has to be the next game."
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