Stoke-on-Trent - Gary Cahill kept Chelsea's title charge on track as the defender's 87th-minute winner gave the Premier League leaders a hard-fought 2-1 victory at Stoke on Saturday.
Willian's cheeky free-kick put Chelsea ahead in the 13th minute but Stoke equalised when Jonathan Walters converted a penalty conceded by Cahill seven minutes before half-time.
Chelsea looked the more likely winners after the break, as Marcos Alonso's free kick hit the crossbar and goalkeeper Lee Grant superbly denied Pedro.
Stoke were never out of the game but Cahill fired home to punish a mistake by Erik Pieters, who failed to clear David Luiz's header from a corner.
Victory for Chelsea made it 12 games unbeaten in all competitions and they are now 13 points clear of second-placed Tottenham, who face Southampton on Sunday.
Stoke's defeat ended their eight-match unbeaten home record going back to a 1-0 defeat to Bournemouth on November 19.
Chelsea were without Eden Hazard after the Belgium international injured a leg muscle in training and Pedro's recall in his place was the only change to the side that beat Manchester United 1-0 in the FA Cup quarter-finals on Monday.
There was no place in the 18 for John Terry, who Stoke boss Mark Hughes admitted enquiring about the last time the clubs met on New Year's Eve, following a minor injury.
Antonio Conte's side broke the deadlock from the first chance of the game.
Marko Arnautovic brought down Pedro for a free kick on Chelsea's left and Willian whipped it in to the near post, the ball seemingly going through a bemused Grant.
Grant atoned for his error by making a superb reflex stop to deny Alonso from point-blank range on the half hour.
Three minutes later, Stoke had an effort disallowed for offside when Saido Berahino was judged to have pushed Nemanja Matic as Bruno Martins Indi headed home after Geoff Cameron nodded Joe Allen's corner back into the six-yard box.
But Stoke fans didn't have long to wait before cheering a legitimate goal when they were awarded a penalty after Cahill shoved Walters at a Pieters free kick.
Walters stepped up to confidently steer home into the roof of the net for his fifth goal of the season.
Chelsea looked to regain the lead and in the 51st minute a superb pass from N'Golo Kante split the Stoke defence for Alonso to gallop onto, but the Spanish wing back's shot was deflected behind.
The leaders were centimetres away from regaining the lead in the 66th minute.
Alonso's curling free kick from 22 yards bounced off the bar and to safety after Pieters was booked for bringing down Pedro.
Two minutes later, Matic's 25-yard drive was smothered by Grant as Chelsea pressed again.
Stoke had Grant to thank in the 76th minute when the keeper produced a superb fingertip save to deny Pedro's fierce rising angled drive.
It looked like heading for a draw before Cahill's late heroics, while Grant denied clean-through substitute Ruben Loftus-Cheek in the third minute of time added on at the end.
Stoke had Phil Bardsley sent off for two bookable offences, both in stoppage time.