Manchester United emerged 2-1 winners against rivals Manchester City on Saturday as Marcus Rashford and Anthony Martial's goals helped their team close the gap to fourth place in the Premier League to five points.
The loss at the Etihad further reduces the defending champions shot to retain their crown, as league leaders Liverpool won earlier in the day. Manchester City are third in the league with Saturday's loss, and Leicester City have the chance to go six points clear o in second if they beat Aston Villa on Sunday.
Rashford opened the scoring with a penalty on 23 minutes after VAR ruled a handball by Bernardo Silva. The goal meant Rashford equalled his season-best tally of 13 in all competitions.
Just six minutes later Martial doubled United's lead by drilling a low shot past Ederson.
A 84th minute header by Nicolas Otamendi off Riyad Mahrez's corner helped pull one back for City, but the furious rally at the Etihad ultimately came short.
The result made it back-to-back wins for Ole Gunnar Solskjaer's side, following Wednesday's 2-1 victory against Tottenham.
The heated rivalry saw plenty of hard fouls and tense moments, most notably when United midfielder Fred was hit with an object from the stands on a corner kick attempt in the second half. The Brazilian player also allegedly suffered racial abuse from a fan.
In the match itself, City had to scramble back into the match after giving up the two first-half goals.
"Us defenders need to hold our hands up," City defender Kyle Walker said. "They have quick players and they are going to hurt you on the counter. They had a game plan and it worked."
City manager Pep Guardiola conceded it wasn't this side's best performance.
"We have to try and improve against teams like this," Guardiola said. "Every week team are looking for these kind of situations.
"We conceded three or four counter attacks. Sometimes we control it, but sometimes we struggle."
United manager Ole Gunnar Solskjaer had measured praise for his side.
"It's been an inconsistent start to the season, it's a young team, and we've been trying to get the right fundamentals and the only way to get consistency is to go through these hard times," he said.
"You have to stick with the manager and process. If we do that we've got something to be excited about in the future.
"I've seen the improvement since I came, the boys have had to reshape the squad, change culture of the squad, the way we want to play."