Guardiola reportedly lost his cool with David Silva, accusing him of not running enough.
City are now 8 points behind PL leaders Liverpool following their 2-0 defeat at home to Wolves on Sunday.
However, cracks were starting to show even before that, with club legend Silva having been given a rollicking by City boss Guardiola after a 12-minute appearance against Tottenham, according to the Mail.
The publication reports that over the summer Guardiola had decided to rein in his famed perfectionist rants at his players, and take a calmer, more relaxed approach.
But after Silva came on in the 2-2 draw at home to Tottenham in August with 12 minutes to go, and failed to influence the scoreline, Guardiola reverted back to his old methods.
According to the Mail, the City boss said: "David, you didn't give us enough running. Where were the legs?