Thirty thousand feet above the Baltic, most of the bleary-eyed passengers aboard Czech Airlines flight 8783 to Manchester were drifting off to sleep as the emotions of the previous night finally caught up with them.

All was quiet, until the peace was shattered by two high-pitched voices that were cheerily broadcasting the song they had just penned about how “that boy John Terry slipped on his bum”. Sir Alex Ferguson was not there to hear it, having been on an earlier flight, but no doubt the Manchester United manager's two young grandsons have regaled him with their new party piece at family get-togethers in the four months since.

Victory over Chelsea in the Champions League final in Moscow, coming barely a week after the successful retention of the Barclays Premier League trophy, seemed to re-establish United as the dominant force in English and European football, but, as has since become clear, it also fuelled a burning desire among Terry and his team-mates to put things right this season.

Under Luiz Felipe Scolari, they have sent out some serious messages of intent. Victory over United at Stamford Bridge tomorrow, to take them nine points clear of the European champions in the Premier League, would be the loudest and most emphatic yet.

Ferguson seemed uncomfortable yesterday when the size of that potential deficit was mentioned. “We don't want to be nine points behind Chelsea,” he said. “We don't want to be nine points behind anyone. So obviously we've got a job to do and the players will be up for it. Obviously, having had a disappointing result last Saturday [losing 2-1 away to Liverpool], we have to do something about it, which is the nature of our football club. When we lose a game we have to do something. We have done that very well over the years and hopefully we'll get it right at Chelsea.”

Getting it right at Stamford Bridge is one thing, but winning there is quite another. No visiting team have beaten Chelsea in the Premier League in 85 matches, since Arsenal's “Invincibles” did so in February 2004. Ferguson, though, sounded bullish yesterday as he assessed United's task. It was understandable that he should draw encouragement from the return from injury of Cristiano Ronaldo, who will make his first Premier League appearance of the season.

More interesting, perhaps, was his assertion that Chelsea may no longer be such formidable opponents without Claude Makelele, who has joined Paris Saint-Germain, and Michael Essien, whose power and athleticism will be missing from their midfield until March after he ruptured an anterior cruciate ligament on international duty with Ghana two weeks ago. “They've started very well this season,” Ferguson said. “They've only dropped two points, which they dropped at home [in the 1-1 draw with Tottenham Hotspur].

“They're maybe a little bit different now without Makelele. He was a very important cog in their machine. The power of Essien isn't there, either. It's not what you would call a daunting task for Manchester United to go there with the ability we've got in our team. I think they know well that Manchester United can go there and win this game on Sunday.”

The inference was that Chelsea, if hardly a soft touch, do not look so formidable without Makelele and Essien. But they do have the towering Michael Ballack back from injury, the indefatigable Frank Lampard and, in John Obi Mikel, a midfield destroyer who is maturing into the player whom Ferguson was devastated to lose in such acrimonious circumstances in 2005 when the young Nigerian, who was with Lyn Oslo at the time, reneged on the contract he signed with United to accept a more lucrative offer from Chelsea. While he cannot yet match Makelele's intelligence or tactical discipline in the holding role, Mikel has not looked a weak link this season.

The Chelsea player who has caught Ferguson's imagination, though, is Deco, the 31-year-old Portugal playmaker whose flair and imagination have brought a different dimension to their midfield. “Deco is the only real difference I can see to Chelsea under Scolari,” the United manager said.

“He's a different type of midfield player to what they've had before. They've relied on the power and athleticism of Essien in that role, but now they have a different type of player - diminutive, clever, nice footballer - and that has made a difference to the way they play.

“We looked at Deco when he was at Porto, but he went to Barcelona for a large sum of money - £24million or something like that. We didn't get involved in that and of course we already had players like Paul Scholes. But he's an excellent boy, no question about that.”

On the evidence of his team's tame surrender at Anfield last Saturday, when they were overpowered in midfield by Javier Mascherano, of Liverpool, Ferguson may be happier if Deco's presence and Essien's absence make tomorrow's match a technical, rather than physical, contest.

With Ronaldo desperate to return to the starting line-up after an impressive 28-minute run-out as a substitute against Villarreal in the Champions League on Wednesday, United have their most likely match-winner available to them again, as well as Dimitar Berbatov, the £30.75million signing from Tottenham Hotspur. Finding a way to accommodate the two, along with Wayne Rooney and Carlos Tévez, promises to be one of Ferguson's biggest challenges this season.

The greatest threat of all, though, is that posed by Chelsea, who, having clicked as quickly under Scolari as they did under José Mourinho, have hit the ground running, while United have stumbled through the opening weeks of the season.

For Terry, it seems that the painful memories of slipping on his bum, as a couple of young Fergusons would have it, have aroused a strong determination to dump the European champions on their backsides.