A crushing defeat was about to be confirmed for Manchester City when Sergio Aguero flew into a knee-high challenge and Fernandinho grabbed a goading opponent by the throat in an ensuing melee, shoving him over an advertising hoarding.
City's players didn't just lose a match to a big title rival. They lost their heads.
In a feisty, action-packed game between two of the Premier League's heavyweights, Chelsea scored three goals in the final half-hour and rallied for a 3-1 win at City on Saturday.
It was an eighth straight victory for the leaders, all of them coming since their coach, Antonio Conte, switched to a 3-4-3 formation that is making the team irresistible going forward. City dropped four points behind Chelsea in fourth place.
Aguero and Fernandinho, two mainstays of Pep Guardiola's City team, were both red-carded in those unedifying final seconds that saw tempers flare and both sets of players pushing and shoving on the field. Aguero is set to miss the next four matches for his lunge on David Luiz, because it was his second sending-off this season.
Diego Costa sparked the turnaround for Chelsea, canceling out a 45th-minute own goal by teammate Gary Cahill with an equalizer in the 60th after chesting down Cesc Fabregas' long ball.
Costa set up substitute Willian to put Chelsea ahead in the 70th and Eden Hazard added a third in the 90th, before Aguero's tackle on Luiz sparked the late skirmishes.
Here's a look at what else happened in the Premier League on Saturday, which ended with Chelsea holding a three-point lead over second-placed Arsenal:
WEST HAM 1, ARSENAL 5
Arsenal forward Alexis Sanchez displayed his mesmerizing skills in scoring a 15-minute hat trick against injury-hit West Ham at the London Stadium.
Arsenal was leading 1-0 through Mesut Ozil's 24th-minute goal, which was set up by Sanchez, when the Chile international began his spree. A brilliant individual effort in the 72nd minute was followed by a low strike from outside the area in the 80th, before he ran through and chipped the goalkeeper to complete his hat trick in the 86th.
Alex Oxlade-Chamberlain was Arsenal's other scorer.
West Ham lost central defender James Collins in the opening minutes, causing a change of formation and extending an absentee list that grew this week with injuries to Diafra Sakho, Aaron Cresswell and Michail Antonio.
Andy Carroll replied for West Ham on his first match back from injury.
TOTTENHAM 5, SWANSEA 0
The respite was brief for Swansea's American coach, Bob Bradley.
A week after finally earning his first win in charge of the Welsh club, Bradley saw his side overwhelmed by Tottenham and return to the bottom of the 20-team standings.
Harry Kane and Christian Eriksen both scored twice for Spurs at White Hart Lane, with Son Heung-min netting the other with an acrobatic strike.
SUNDERLAND 2, LEICESTER 1
Leicester lost for the seventh time in 14 matches of its disappearing title defense.
Jermain Defoe's eighth goal of the season ultimately condemned Leicester to a defeat that kept the champions two points above the bottom three.
Sunderland is still in the relegation zone despite winning three of its last four games.
Defoe struck in the 77th minute after Robert Huth's own goal gave the home side the lead at Stadium of Light in the 64th. Substitute Shinji Okazaki pulled a goal back for the visitors in the 80th.
Crystal Palace beat Southampton 3-0 thanks to two goals by Christian Benteke and another by James Tomkins, ending a run of six straight losses that had heaped pressure on manager Alan Pardew.
West Bromwich Albion won 3-1 at home to Watford and climbed into sixth place, ahead of Manchester United's match at Everton on Sunday.
Stoke beat Burnley 2-0.