Squads richly assembled by Roman Abramovich and Abu Dhabi's Sheikh Mansour, one of the few men in the world with more disposable cash than the Russian oligarch, do battle at Stamford Bridge in one of the most eagerly anticipated contests of the season.
"You have to say that," said Mourinho, when asked if City should be considered favourites.
"You (the media) said that in 2004 and 2005 (about Chelsea). Now it's up to you to say yes or no."
City have "two very good teams" Mourinho says.
"One playing and another one on the bench and in the stands," he added.
But the visitors will be without one of their most influential players in injured captain Vincent Kompany.
With the options at their disposal, Mourinho does not believe Kompany's absence will be significant.
"It's a surprise for me, because I thought he was going to play, but it doesn't change (anything)," Mourinho added.
Despite praising the City squad, Mourinho is not jealous of Pellegrini's options, who preceded him as Real Madrid boss.
"I'm not an envious person," he said.
After his Bernabeu exit, Pellegrini revived himself at Malaga before joining City.
Mourinho has said he would not have made a similar move.
Asked why, he said: "I am in a situation where I can choose.
"Some people can't choose. If in this moment I decide to stop football, I stop football. Just that.
"But no offence against him, no offence against Malaga."
Now Pellegrini is bidding to help City claim a second Premier League title.
City are a point behind Chelsea after eight games and Mourinho believes Sunday's contest will have a limited impact come the end of the season.
Asked what will be the difference in May, the self-proclaimed 'Special One' said: "Everything and everybody. The medical department that recovers a player one week (ahead of schedule); the board that gives great support and great stability; the supporters that travel away to support the team; the supporters at home that are very strong in the way they support; the manager that is more or less talented to help the team in some difficult moments; a little bit of luck also plays a part.
"All of this together, and at the end of May, somebody will be champion."
The period before Christmas could have a major bearing, though, and Chelsea's challenge has unravelled prior to the new year in recent seasons.
Mourinho said: "I'm not looking to November, December, I'm looking to tomorrow and tomorrow is still October. After, we will see what happens.
"I don't believe in curses. We have matches to play, lots of matches.
"We have six matches in November, plus the Capital One Cup match, which is the end of October, plus two matches in the national teams, which makes nine.
"Nine matches in a month. For sure we can't win nine. That's for sure. Maybe we lose, maybe we draw.
"For sure we keep the balance. The same way we keep the balance when we lost against Basle."
Then perhaps as a reminder to Pellegrini that he is a seasoned campaigner in title fights, Mourinho said: "Experience helps."