Pep Guardiola suffered the largest league defeat of his managerial career as Manchester City were thrashed 4-0 by Everton, while Zlatan Ibrahimovic's late equaliser gave Manchester United a 1-1 draw with Liverpool on Sunday.
Goals from Romelu Lukaku and Kevin Mirallas put Everton in control at Goodison Park.
Teenager Tom Davies scored a fine first goal for Everton in the closing stages and debutant Ademola Lookman completed the rout after coming on as an 89th minute substitute.
It was another chastening experience for City boss Guardiola, who wasn't used to such humiliation in his trophy-laden spells at Barcelona and Bayern Munich.
The defeat was City's fourth in their last eight league games and left them 10 points behind leaders Chelsea.
Publicly at least, Guardiola wasn't angry with his expensively assembled team and he insisted the chastening afternoon could have gone differently if City had taken their early chances.
"We created enough chances in the first half to score. After what happened we were not able to score and Everton had one chance and scored," Guardiola said.
"They scored straight after half-time and that is tough mentally for the players."
But the Spaniard did concede City look destined not to win the title in his first season in England.
"The first one, yeah," said Guardiola when asked if top spot is now out of the question.
"The first one is a 10-point gap and that is a lot of course."
United manager Jose Mourinho had called for his club's fans to turn up the volume after some subdued atmospheres at Old Trafford recently.
But Jurgen Klopp's side silenced the home supporters when James Milner converted a 27th minute penalty awarded for Paul Pogba's needless handball.
Liverpool goalkeeper Simon Mignolet made fine saves to keep out Ibrahimovic's free-kick and a Henrikh Mkhitaryan strike as United pushed for an equaliser.
Not for the first time, Ibrahimovic was United's saviour as the Swedish forward struck from close-range in the 84th minute for his 19th goal since his free transfer from Paris Saint Germain in the close-season.
There was a heated finale as Mourinho and Klopp argued on the touchline after United's Ander Herrera grappled with Liverpool's Roberto Firmino.
The feuding managers were eventually separated and exchanged a brief handshake at the final whistle.
Liverpool's draw meant they lost ground in the title race, leaving them seven points behind Chelsea in third place.
Klopp's team have now gone four games without a win in all competitions.
United remain sixth after their six-match winning run in the league was brought to an end.
Mourinho's men are 12 points behind Chelsea and four points adrift of the top four.