The reigning Premier League champions have had a tough run this season, most recently losing 4-2 to Paris Saint-Germain on Wednesday despite leading the game 2-0.
In the league their fortunes have turned for the better as they are undefeated in five matches but from November to December Man City won only one out of nine matches.
Guardiola dominated English football for years, winning six titles, four consecutively from 2021 to 2024.
But this season has been arguably his worst ever campaign as a manager as his tactical weaknesses have been brought to the forefront.
"Everyone came to the Etihad and stayed back," he said.
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"The first team I saw man-marking was Neil Warnock at Cardiff. Now everyone does it.
"Everyone comes here, it doesn't matter, man to man.
"They just jump to Ederson or Stefan [Ortega]. You have to adapt, do it better with the ball, otherwise you are not qualifying for the Champions League."
Currently Man City sit in a Champions League elimination spot with their next match against Club Brugge being a must-win to progress in the competition.
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"Speed is important but against PSG we ran more than them," he said.
"Our problem is with the ball. This season is what we have missed.
"If you have the ball and don't pass properly to your mate, everything is so difficult."
Man City's three new signings: Abdukodir Khusanov, Vitor Reis and Omar Marmoush may be the key to going on an extended run of good form.
Eyes will be on Marmoush especially, who cost Man City £59m - a price tag that will lead fans to expect some goals.
At Eintracht Frankfurt this season he had 15 league goals in 17 matches, with 10 assists as well before moving to the Etihad Stadium.
"There are seasons when there are a lot of difficulties," Guardiola said.
"How do you stand up? How do you stay there?
"I remember Jose (Mourinho). I don't know the reality of United but he said many times finishing second in that season was his biggest success. I understand completely."
Man City are fifth, 12 points off first place Liverpool, and six behind second place Arsenal.
It may be too late for a fifth consecutive title but as we've seen multiple times Man City are capable of going on crazy winning streaks to end the season.