Jack Grealish and Riyad Mahrez came off the bench to combine for the goal that earned Manchester City a 1-0 win at Chelsea, taking the champions within five points of leaders Arsenal.
Chelsea suffered early setbacks as Raheem Sterling and Christian Pulisic added to the club's growing injury list, limping off in the opening 22 minutes.
But Pulisic's replacement Carney Chukwuemeka almost put the hosts ahead, when his deflected effort struck a post.
Guardiola made two half-time changes, bringing on Manuel Akanji and Rico Lewis, and his side took charge of the match.
Nathan Ake nearly scored against his former side, with his headed attempt from a Kevin De Bruyne cross coming back off the woodwork.
With City still looking for a breakthrough on the hour-mark, Pep Guardiola introduced wingers Grealish and Mahrez, and the pair promptly combined for the decisive goal in the 63rd minute, with Grealish crossing for Mahrez to tap in at the back post.
The victory moves the champions on to 39 points, while Chelsea are 10th on 25 points.