Sarri's charges were the first to beat City in the Premier League this season, with goals from N'Golo Kante and David Luiz condemning the reigning champions to a 2-0 defeat at Stamford Bridge in early December.
Further defeats to Crystal Palace, Leicester City and Newcastle United proved that Guardiola's men are indeed fallible, but recent results have seen them return to the summit of the English top flight, pipping Liverpool on goal difference.
And while Sarri is one of the few managers to get the better of Pep this season, he admits that repeating the feat at the Etihad Stadium on Sunday will be no easy task.
“I think we were lucky [in the last match vs City] because we scored in a very difficult moment in the match,” the Italian told a press conference on Friday.
“Maybe we deserved to win in the second half, but we were very lucky in the first. In that match we defender very well as they only had three opportunities on goal, no more.
“It's not easy against City to limit them to three or four opportunities – they had scored 43 goals in 15 matches, so it's difficult and we need to defend well.
“I was happy with the result and the performance, now we need consistency. I hope that on Sunday we'll be the best version [of ourselves].
Regarding his gameplan, Sarri added: “We need to be very fast when we're recovering the ball. They are able to press really well and it's difficult to find a way out of that situation.
“If we can do that, we can do well.
The Chelsea boss has been tasked with recovering the west London club's status as title challengers, but he claims there is a lot of hard work to do before they can get close to City or Liverpool's level.
“We need to reduce the gap,” he said. “We need to work. You can either be the most competitive in the market or you can work. I don't know any other way.
“The Premier League is very difficult. It's not easy to win or even get to the Champions League. We need to work, but I think they [Man City] are an example for every club.
“I think they are the best team in Europe.
“At the moment I don't think [we are title contenders]. I think we can fight for the top four this season, no more. We can win something, of course, but the Premier League is now a fight between Manchester City and Liverpool.”
Pressed further as to whether Chelsea can match City at some point in the future, Sarri simply replied: “I think so.”