The Londoners are six points ahead of United with 10 weeks of the season left and ahead of their trip to struggling Norwich on Saturday, Chelsea striker Didier Drogba said: "We have won the title. This season we are the best."

But United, before Chelsea kick-off on Saturday, can close the gap to three points if they win away at Crystal Palace, still battling for Premiership survival.

And Ferguson said Friday that while last weekend's League Cup final win over Liverpool was clearly good for Chelsea's confidence, Jose Mourinho's side still had work to do before bringing what would be a first top-flight title in 50 years to Stamford Bridge.

"Some Chelsea players have been talking about how they have won the league. That's a bit pre-emptive," said Ferguson.

"Chelsea may look upon these games as easy but we have been there and I can tell them, no matter who they are playing, they are not.

"It's a bit bullish with 10 games to go because football can be a cruel game. I don't know whether it is all confidence or bravado, or if they are just trying to convince themselves - but I do know it could backfire on them.

"They are talking about an easy three points at Norwich, which it may be, but I would never say that when you are playing against teams who are fighting against relegation and trying to survive.

"The one thing you do expect when you are playing these teams is that they are going to fight.

"We are approaching our game against Crystal Palace believing it will be tough. No game is easy at this time of year."

"Look at Crystal Palace. They are four points in front of Southampton, which is only a little cushion but gives them something worth fighting for.

"People may say it won't make much difference if we pull the gap back to three points but the key thing is that it could and it wouldn't do our confidence any harm either."

Meanwhile Ferguson believes Old Trafford rising stars Wayne Rooney and Cristiano Ronaldo have it in them to become the best players in the world.

England striker Rooney, 19, and Portugal winger Ronaldo, 20, have both made major contributions to United's run of 14 wins in 16 games.

Ferguson said he believed his dynamic duo could join Ronaldinho, the man he missed out on, as the best footballers around.

"We are very fortunate to have these two young players. They are both in fantastic form at the moment and along with Ronaldinho, I think they will become the best players in the world in a couple of years' time."

Rooney has scored 15 goals, including two in last weekend's win over Portsmouth, but Ferguson has been equally impressed by Ronaldo, adding the tricky wide player didn't get the protection he deserved.