Sir Alex Ferguson has lit the blue touchpaper four weeks before the new season by claiming that Chelsea's squad may have already peaked and that Luiz Felipe Scolari will struggle to exorcise the ghost of José Mourinho.

Although Ferguson believes that Chelsea represent the biggest threat to his team's chances of retaining their Barclays Premier League crown, the Manchester United manager suggested that Scolari, newly installed at Stamford Bridge, will be hard pressed to match, let alone surpass, Mourinho's achievements as he wrestles with an ageing squad. Scolari is less than a month into the job, but already the mind games have begun.

Speaking during United's pre-season tour to South Africa, Ferguson said: “I'm not concerned about Chelsea. Mourinho won the title two years in a row and beat us in the FA Cup Final [in 2007, as well as winning two League Cups], so there's no one who can improve on his record really.

“It would have to go beyond Mourinho's performance to really worry us. It will be a challenge with the players they've got and the players they've added - they've got a lot of experience and that was the one thing I was a bit concerned about - but I don't know how far that team has got to go.”

Ferguson believes the wealth of experience in Chelsea's squad will stand them in good stead in the short term, but he is convinced that, in contrast to his own players, they have already fulfilled their potential.

Although the average age of the Chelsea team sent out by Avram Grant, Scolari's predecessor, in the Champions League final in Moscow in May was only marginally higher than that of the United side fielded by Ferguson - 28.45 compared to 27.45 - United have a noticeably more youthful set-up. The average age of United's recognised first-team squad is 25.43 compared with Chelsea's 27.32. In addition, Chelsea possess nine players aged 30 or over, including Deco, who joined from Barcelona last month, while United have only five players in that category.

“Scolari is fortunate,” Ferguson said. “He is joining a big club and a team of internationals, so in that respect it's not an issue at all, but it's hard to see where there's going to be a big improvement with a team that's really very experienced. Maybe [they've] plateaued in a way. How can they accelerate beyond what they've done up to now when you see the ages they've got?”

Other than John Obi Mikel, 21, and Salomon Kalou, 22, Chelsea have no established first-team players under 25, while United boast Anderson, Nani, Wayne Rooney, Cristiano Ronaldo, Carlos Tévez and Darren Fletcher, a factor that Ferguson believes could tell in the coming seasons.

“They've got Kalou and Obi Mikel who are young and Petr Cech [at 26] is a fantastic goalkeeper,” Ferguson said. “I'm not saying necessarily they're [an] old [team] because with the modern-day training methods, you should be playing in your thirties, but I don't see outstanding progress in a team that's in their thirties.”

Ferguson's comments drew an immediate response from Chelsea. Michael Essien, the midfield player who signed a new five-year contract yesterday, said: “For me, only Chelsea will be up there in May. Chelsea will win the title this year. I think we've got a lot of the best players in the world and the boss is going to help us.”

Ferguson believes one of the biggest obstacles to United retaining their title is the fixture list, with Portsmouth, Liverpool, Chelsea, Blackburn Rovers and Everton to play away before November, in addition to the European Super Cup match against Zenit St Petersburg in Monaco on August 29 and the Club World Cup in Japan in December. “We will have to be good,” Ferguson said.