Guardiola took charge at City in 2016 and finished his debut season without a trophy for the first time in his managerial career before leading City to a record points haul last season in their league triumph.
"He (Guardiola) was lucky. I think that, if you choose Guardiola, you have to wait because the club knows very well that Guardiola needs time," Sarri told reporters ahead of Sunday's League Cup final between the two teams.
"It's not really very easy for an English team to play that kind of football, so it's normal."
Chelsea had looked like title contenders when the Italian guided them to a 12-game unbeaten Premier League run but six defeats in their last 14 league games -- including a 6-0 reverse at champions City -- has seen the club drop out of the top four.
Sarri said he did not know if his job at the club was under threat and stressed on getting a result in what is the first final of the season.
"In the end, the most important things are the results. In my job, I need the result, nothing else. I don't know if I am under pressure from my club," Sarri said.
"It's important to win the final, otherwise you are second. I think it's very important for us because we have to find the confidence."
(Reporting by Rohith Nair in Bengaluru)
