London: Chelsea were given a stiff examination by Stoke City at Stamford Bridge on Saturday before extending their lead at the top of the Premier League to nine points ahead of the late game between Liverpool and Manchester City.
Willian scored twice as a spirited Stoke were beaten 4-2 despite twice coming back to equalise.
That made 13 successive victories for Antonio Conte's side, equalling the record by any club for a single season in the top division of English football.
They were pushed hard, however.
After defender Gary Cahill headed in a corner, Dutch international Bruno Martins Indi brought Stoke level. Willian then scored twice in eight minutes in the second half, on either side of Peter Crouch tapping in for his first Stoke goal since May 2015.
Chelsea could not feel secure until Diego Costa, back after suspension, scored his 14th of the season.
Sixth-placed Manchester United fell behind at home to Middlesbrough before goals from Anthony Martial and Paul Pogba in the last five minutes brought about a 2-1 win.
Aitor Karanka had proved a match for his mentor Jose Mourinho, under whom he once worked at Real Madrid, and Grant Leadbitter scored for the visitors midway through the second half after Alvaro Negredo nodded down a cross for him.
It was Middlesbrough's first attempt on target.
Zlatan Ibrahimovic, with 11 goals in his previous 10 games, was annoyed to have a 12th ruled out in the first half, for a high foot.
Martial, who had earlier hit a post for United, brought them level with only five minutes to play and a minute later Pogba earned United their fifth successive league win.
West Bromwich Albion moved above Southampton into eighth place by coming from behind to beat them 2-1 at St Mary's.
The home side led just before halftime when Irish international striker Shane Long scored against his old club but Albion equalised within two minutes through Matt Phillips.
Only four minutes into the second half Hal Robson-Kanu marked his first start of the season by thrashing in a winning goal.
Having lost late on in their previous away games at Chelsea and Arsenal, Tony Pulis's team were able to hold on this time, as Southampton's coveted defender Virgil van Dijk received a red card.
Leicester City, who had made the worst start of any champions for more than half a century, won an entertaining game 1-0 at home to West Ham United.
With England striker Jamie Vardy suspended, Algerian Islam Slimani headed the only goal to end the London side's improved run of three successive victories.
Swansea City, who sacked manager Bob Bradley earlier this week, slumped to a 3-0 home defeat by Bournemouth to leave them bottom of the table at the halfway stage of the season.
Benik Afobe, Ryan Fraser and Josh King were the scorers as Bournemouth moved back into the top half of the table.
Sunderland stayed in the relegation places with a heavy 4-1 defeat at Burnley, whose impressive home form continues to make up for having taken only one point all season on their travels.
Andre Gray scored a hat-trick in 22 minutes and Ashley Barnes added a penalty before Jermain Defoe's late reply.
Sunderland have 14 points, two more than Swansea and one more than Hull City, who moved off the bottom with a 2-2 draw against Everton on Friday.
In the remaining weekend fixtures on Sunday, fourth-placed Arsenal have a London derby at home to Crystal Palace and fifth-placed Tottenham visit Watford.