Di Matteo is determined to translate last season's Champions League and FA Cup double into success in the league.
But last season the Blues finished in sixth place, 25 points behind champions City and second placed United, following an erratic league campaign.
Di Matteo, who was installed as permanent manager this summer, believes it will be a tough challenge to gatecrash the title race, particularly for a team in a state of transition.
Yet the Italian knows the demands for success at Stamford Bridge will remain high and he must deliver in the Premier League to keep his job, with former Barcelona coach Pep Guardiola believed to waiting in the wings.
"This is an ambitious club and we know we have to win trophies to be successful," Di Matteo said.
"Personally, I still believe that Man City is the favourite because they haven't lost any key players. But, certainly, Robin Van Persie is a good signing for United.
"We have to try to close the gap, for sure. It's not that we're not going to try.
"We have to try to challenge ourselves with the other teams, so I wouldn't say there is no expectation."
Di Matteo's squad has undergone a significant overhaul since that dramatic Champions League final win over Bayern Munich.
Out have gone Didier Drogba, Jose Bosingwa and Salomon Kalou, with Eden Hazard, Oscar and Marko Marin coming into the club.
Di Matteo expects the new look of the squad to be reflected in a changing style of play for a team that relied heavily on Drogba's power last season.
Marin will be missing with a hamstring problem on Sunday, but otherwise Di Matteo has a full strength squad to choose from, including Oscar who has just joined up with the club after his Olympic campaign with Brazil.
More arrivals are expected, possibly including Victor Moses who will line up for Wigan on Sunday after several Chelsea bids for the Nigerian forward were rejected by the Latics.
Wigan manager Roberto Martinez is confident Moses will be ready to face players who could soon become team-mates.
"If you don't meet a valuation, it becomes paper talk and speculation," he said.
"It happens everywhere, it gives you uncertainty and I don't think that helps. The players are human beings.
"For Victor it's been an exciting summer. I told him he should be very proud, as a footballer at 21, to get the interest he has had.
"Victor knows what he did from December to the end of the season was a great level of performance.
"He can take it on to the next level and I am very excited to have him at Wigan, and I hope we can keep him for many years to come."
Wigan are embarking on an eighth straight season in the top flight after winning their last four home games last term to beat relegation.
And Martinez, who had talks with Liverpool about taking over at Anfield in the summer, is demanding his new-look team continue from where they left off when they face Chelsea.
Striker Arouna Kone is set to start after arriving from Spanish club Levante after scoring 15 goals in La Liga last season.
Ryo Miyaichi could also figure after signing on loan from Arsenal but defender Ivan Ramis, who has joined from Mallorca, is struggling with a hamstring injury.
Source: AFP
Source: AFP