Chelsea left it late at the bet365 Stadium, but eventually came away with three points after beating Stoke City 2-1.
Willian opened the scoring for the league-leaders with a first half free-kick, but Jonathan Walters responded before the break by converting a penalty after Gary Cahill had fouled Walters.
Marcos Alonso hit the bar in the second half as the visitors probed for a second goal.
Cahill was to make up for giving away the penalty however as he smashed home a corner to steal the three points with five minutes left.
Phil Bardsley was sent off in the closing stages for a second yellow card.
Diego Costa had looked to be in one of those moods from the start as he clashed with Ryan Shawcross, Geoff Cameron and Bruno Martins Indi and got short shrift from referee Anthony Taylor each time.
The man in the middle was rightly interested when Marcos Alonso was bundled over by Marko Arnautovic around five yards from the right-hand side of the box.
It looked like the perfect opportunity to deliver a cross, but Willian had other ideas and whipped his free-kick around the two-man wall and past Lee Grant, who should have done better than to just help the shot on its way in.
Not even that could improve Costa’s demeanour, though. He threw himself to the ground once more and popped up to rant at Taylor when he did not get a free-kick, earning a caution for dissent in the process.
Already Antonio Conte seemed sufficiently concerned about his striker’s mental state as he sent Michy Batshuayi out to warm up.
Grant prevented it from becoming 2-0 by parrying Alonso’s effort and Stoke thought they had levelled in the 34th minute when Joe Allen’s corner was headed on by Cameron and then into the net by Martins Indi.
However, the assistant’s flag went up – possibly for offside against Saido Berahino, who could also have been punished for a push on Pedro. Whatever the reason, the goal did not stand.
And Stoke benefited from a contentious call three minutes later having been given a penalty as Walters went to ground having been nudged there by Cahill.
The decision could have been construed as soft but the spot-kick certainly was not as Walters lashed in the leveller.
Pedro blazed over a good chance to restore the visitors’ lead before Bardsley clattered into Costa to be booked in the final stages of a tempestuous half.
A 15-minute cooling off period eased the simmering tension and Chelsea started the second half brighter with Alonso only stopped by a terrific Bardsley challenge and David Luiz’s 40-yard free-kick almost catching Grant out.
The Potters keeper looked uncomfortable at set-piece situations, although there was little he could do but be thankful Alonso’s 25-yard effort struck the crossbar.
Grant was up to the task when called on next as he made a brilliant one-handed stop at the near post to deny Pedro once he had been slipped in by Willian.
It was far from relentless from the leaders but when the opportunity to win it fell to Cahill, the Blues skipper snatched it.
Erik Pieters conceded a needless corner with a poor back-pass to Grant and the Dutchman’s clearance from Luiz’s header came to Cahill to fire home.
Costa struck a post after that yet he was a footnote in this contest, even when the red card came out, with Bardsley the recipient for a second cautionable offence as he fouled Cesc Fabregas.
The Chelsea celebrations at full-time suggested they appreciated the magnitude of a victory which inched them ever closer to a seemingly inevitable title triumph.