Manchester City trimmed the gap between them and the Premier League leader Arsenal to five points by beating Chelsea 1-0 after a double substitution by Pep Guardiola paid off immediately at Stamford Bridge.
Riyad Mahrez and Jack Grealish entered in the 60th minute and combined for the only goal three minutes later, with Mahrez tapping in from close range after a perfectly weighted cross by his fellow winger.
City only came to life in the second half after a curiously passive display before halftime, perhaps brought on by a confusing team selection by Guardiola that saw a number of players deployed in unusual roles.
Known for his overthinking at times, Guardiola accepted after the game he got it wrong. That's why he took off two full-backs - Joao Cancelo and Kyle Walker - at halftime and restored Rodri to centre midfield, with the Spaniard having also been in a hybrid role covering central defence, too.
Suddenly, City were all over Chelsea and creating chances, even if top scorer Erling Haaland was largely kept quiet and Kevin De Bruyne shone only fleetingly.
Guardiola reserved special praise for halftime sub Rico Lewis, 18, because he changed the game.
The goal came after Guardiola's second double change, though it might have been kept out had Chelsea goalkeeper Kepa Arrizabalaga stretched out to block Grealish's low cross from the left rather than pull away his arm.
City pulled four points clear of third-place Newcastle and closed in on Arsenal, who drew 0-0 at home to Newcastle on Tuesday.
Chelsea stayed in 10th place, 19 points off the leaders. Graham Potter's team is as close to the relegation zone as the top four.
Chelsea lost forwards Raheem Sterling, who joined from City in the offseason, and Christian Pulisic to injuries in the first half. Pierre-Emerick Aubameyang came on for Sterling in the fifth minute and was substituted in the 68th.
Another of the substitutes, Carney Chukwuemeka, struck a shot against the post at the end of the first half.
The teams meet again in the FA Cup on Sunday, with City hosting on that occasion.
