Pep Guardiola expects Chelsea to be back challenging for the title in the near future.
Chelsea last won the Premier League during Guardiola's first season at Manchester City in 2016-17.
Since then it is City who have dominated the competition, taking the crown in five of the past six campaigns.
Chelsea did edge out City in the 2021 Champions League final but there has been plenty of turbulence at the London club since, and they currently sit 10th in the table.
Guardiola, who takes his side to Stamford Bridge on Sunday, said: "Chelsea remain one of the more important teams in England.
"It’s true that in the Premier League they were not close to winning it in these last seasons but they’re still one of the strongest teams, there’s no doubts about that.
"I see that in the last games they are alive, they have good spirit, they are aggressive, they have a good pattern. The quality is there.
"It’s one of the toughest games that we have during the season. Sooner or later Chelsea will be there fighting for the titles, and I guess sooner than later."
Chelsea have had a rocky start to the campaign under new manager Mauricio Pochettino but Guardiola has no doubt they will come on strong.
He said: "It’s normal. They are getting better. Every manager needs his time – it’s a new club, new players but they’ll be a top contender because the quality in all departments is there."
Two of Chelsea’s better performers this season have been the former City pair of Cole Palmer and Raheem Sterling.
City academy product Palmer, 21, switched clubs in August having grown frustrated at a lack of opportunities at the Etihad Stadium.
Guardiola said: "The reason why was that he wanted game time. Now he has it, so congratulations.
"He’s a guy who came from the academy and if he is having success it’s good for him and we wish him the best. I’m really pleased for him."
Sterling won four Premier League titles and the FA Cup at City and Guardiola recognises him as a dangerman this weekend.
Guardiola said: "He’s playing really good, he’s back in his best moments, best performance, (from) what I’ve seen lately.
"He always creates incredible dangers for the opponents."
Guardiola also said he has no issues selling players to rivals because Manchester City are not a "small club".
The champions come up against two of their recent former players in Cole Palmer and Raheem Sterling today.
Palmer left City for Stamford Bridge in August having grown frustrated at a lack of game time under Guardiola, a year after Sterling also moved there for a fresh challenge.
Both went with the club's blessing, as did Gabriel Jesus and Oleksandr Zinchenko when they joined Arsenal – and fuelled a strong charge at City’s crown – last year.
Some managers might be uncomfortable with at sales that effectively strengthen clubs in direct competition, but Guardiola insists it has "never ever" bothered him.
The City boss said: "From my point of view, I give my opinion to the club but after that the club has to decide if the transfer is good for both sides and for the player.
"But never ever (has it been an issue). I think that means you are a small club. Big clubs make decisions for the benefit for all three parties: players, both clubs – and agents sometimes. Really, it’s not a problem.
"So if they want to go to Chelsea or (Manchester) United or, I don’t know, Liverpool or whatever, what is the problem? They are happy to be there, the club is happy for the transfer.
"Another player would come and we’d keep going: good spirit, good mood, and try to do it."
City had high hopes for 21-year-old midfielder Palmer, who came through their youth system.
He was a member of the squad that won the treble last season and started the current campaign strongly with goals in the Community Shield and European Super Cup matches.
It looked like he could get more opportunities following the departure of Riyad Mahrez but he opted to move on regardless, joining Chelsea in a £42.5million deal.
So far he has impressed at the London club and Guardiola accepts his decision to move appears to have paid off.
He said: "They moved from here because they wanted to play and, if they play, the decision made has been good.
"So Raheem, since he left, plays always and Cole, since he left, is playing always. So they took good decisions.
"Cole accepted some process but after one or two years he said, 'I don’t want to stay here because I’m not going to play’.
"I said, ‘But Riyad is leaving, you have a chance’. He said, ‘I’m not going to play here. I’m going to leave’.
"OK, leave. He got what he wanted. It’s good for him. He’s a huge talent. Otherwise he would not have been here."
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