City are playing their third game in just over a week but weren't showing any fatigue in the first-half against Chelsea, as they dominated the ball and controlled the game.
Despite all their possession, however, the Blues had struggled to fashion many clear-cut chances and Frank Lampard's side were looking more dangerous on the counter.
Then they hurt City in clinical fashion in a counter-attack from a free-kick, though they were helped out not once but twice by Mendy.
As Chelsea cleared the ball the Frenchman went to gather it but then he played a wayward pass which was intercepted by Christian Pulisic, who broke with pace.Mendy managed to catch up with the American but made his second mistake as he dived in for a tackle, which Pulisic.
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