Chelsea's week to forget ended with a day to forget on Saturday as their advantage at the Premier League summit was trimmed to five points by resurgent champions Manchester City.
Tarnished by the incident last Tuesday that saw a group of the club's fans prevent a black man from boarding a Paris Metro train while chanting racist songs, Chelsea were held to a frustrating 1-1 draw by lowly Burnley.
Ben Mee claimed an 81st-minute equaliser for Burnley after Nemanja Matic had been sent off for lashing out at Ashley Barnes and City took full advantage by cruising to a 5-0 home win over Newcastle United.
On their pre-scheduled 'Equality Day', Chelsea warmed up in T-shirts bearing anti-discrimination logos and took a 14th-minute lead when Branislav Ivanovic scored after a weaving run from Eden Hazard.
It was the Serbian defender's second goal in two matches following his equalising header in the 1-1 draw at Paris Saint-Germain and seemed destined to restore a sense of normality to Stamford Bridge.
But after his countryman Matic was shown a 70th-minute red card for retaliating when Barnes caught him on the shin with an ugly challenge, Mee headed home Kieran Trippier's left-wing corner to equalise.
Chelsea manager Jose Mourinho felt his side should have been awarded four penalties, telling his post-match interviewer: "There are four moments of the game where you can write the story: minutes 30, 33, 43 and 69.
"Don't ask me more questions. I can't go through the incidents. I am punished when I refer to these situations and I don't want to be punished."
While Mourinho seethed, City set about dismantling Newcastle 5-0 in a sparkling performance that set them up perfectly for Tuesday's Champions League visit of Barcelona.
Edin Dzeko won a penalty inside 30 seconds after being clipped by Vurnon Anita and Sergio Aguero scored from the spot to put City ahead.
Samir Nasri stretched City's lead before Dzeko added a glorious third in the 21st minute, chesting down a raking pass from David Silva and steering a left-foot shot past Tim Krul.
Silva got in on the act with a brilliant quick-fire brace early in the second half and Wilfried Bony gave City's fans further reason to cheer when he came on to make his debut.
"I'm very pleased because we returned to (being) a scoring team and did not concede goals," City manager Manuel Pellegrini told the BBC.
"Four goals were wonderful play and the first goal was good play as well. It is very important to arrive for the Barcelona game having won today (Saturday)."
Arsenal leapfrog United
Manchester United lost momentum in the battle for Champions League places after seeing a 19-game unbeaten run come to an end in a 2-1 defeat at Swansea City.
Ander Herrera put United ahead in the 28th minute, but Ki Sung-yueng swiftly equalised and Swansea completed a first league double over their opponents when Jonjo Shelvey's shot flicked in off Bafetimbi Gomis in the 73rd minute.
"Today (Saturday), we were the unlucky team," said United manager Louis van Gaal. "I think we created enough chances. We were the dominant side in both halves."
Arsenal capitalised on United's slip-up with a 2-1 win at Crystal Palace that saw Arsene Wenger's side climb to third place in the table.
Santi Cazorla opened the scoring with an eighth-minute penalty after Pape Souare was adjudged to have fouled Danny Welbeck.
Olivier Giroud added a second on the stroke of half-time, following up after Julian Speroni had saved from Welbeck, before Glenn Murray tapped in a stoppage-time consolation for Palace.
United will drop out of the Champions League places if fifth-place Southampton avoid defeat at home to Liverpool on Sunday.
Elsewhere, Tim Sherwood's tenure as Aston Villa manager began with a cruel 2-1 loss at home to Stoke City that saw his new side slip below Burnley to second-bottom.
Scott Sinclair headed Villa in front in the 20th minute, but Mame Biram Diouf equalised and Victor Moses gave Stoke victory with a stoppage-time penalty after Ron Vlaar was dismissed for felling Diouf.
Perennial troublemaker Joey Barton was sent off for flinging a hand towards Tom Huddlestone's nether regions as Queens Park Rangers lost 2-1 at relegation rivals Hull City.
Nikica Jelavic volleyed Hull ahead and although Charlie Austin headed in a 39th-minute equaliser shortly after Barton had been given his marching orders, Dame N'Doye gave Hull victory with an 89th-minute header.
In the day's other game, Sunderland and West Bromwich Albion played out a drab 0-0 draw at the Stadium of Light.