Manchester City extended their Premier League lead on Saturday while another lacklustre performance dropped Manchester United further behind their neighbours.
City beat Bournemouth 3-1 to go five points clear of Liverpool, who host Everton on Sunday.
Bernardo Silva, Raheem Sterling and Ilkay Guendogan scored for the champions, who had to work for their sixth straight league win.
"People think it's easy for us but that is not the truth so I like to win in this way," manager Pep Guardiola told the BBC.
"Sometimes it happens. It is a lesson we have to learn, how to win when we are tired."
United, meanwhile, had to fight back to draw 2-2 at relegation-threatened Southampton.
Despite overcoming an early two-goal deficit, United now find themselves 16 points behind City after 14 games and six points off a Champions League spot.
"I think it was not the result we wanted," manager Jose Mourinho told BT Sport, though he did have some praise for his side.
"Good spirit, good fight, good comeback to 2-2. A great example of players fighting."
Silva put champions City in front at the Etihad Stadium but Bournemouth equalized through Callum Wilson's header just before half-time.
Sterling then restored the lead in the 57th minute and Guendogan added a late third to send Bournemouth to a fourth straight loss.
Seeking their first home win, Southampton made a dream start with goals from Stuart Armstrong and Cedric in the first 20 minutes.
But United fought back to level before half-time through Romelu Lukaku and Ander Herrera.
Neither side mounted much pressure after the break, leaving Southampton third-bottom of the table with just one win.
"At 2-0 up we had a foothold," Saints winger Nathan Redmond said. "We're kicking ourselves that we couldn’t manage the game better."
Leicester City's good form continued with a 2-0 home win over Watford, who had Etienne Capoue sent off late.
Jamie Vardy and James Maddison scored as the Foxes made it five games unbeaten to sit eighth.
Crystal Palace beat Burnley 2-0 for their first home win this term.
Goals from James McArthur and Andros Townsend gave Palace their first victory in nine games and extended Burnley's winless run to eight.
Javier Hernandez's brace led West Ham to a convincing 3-0 win at Newcastle, who had won three straight, while Brighton came from behind to beat 10-man Huddersfield 2-1.
Mathias Jorgenson scored after 55 seconds, the fastest goal in the league this season, to give Huddersfield an early lead.
Steve Mounie was then sent off and Brighton took advantage as Shane Duffy levelled in first-half stoppage time and Florin Andone won it with a 69th minute header.
"When they went down to 10 men you have to try to capitalize on that," Brighton boss Chris Hughton said.
"It is difficult when you are the team with 11 men but we made the extra man show and Florin Andone's goal was excellent."
A pair of London derbies are also on Sunday's schedule with Chelsea hosting Fulham and Tottenham visiting Arsenal.