Juan Mata's EFL Cup winner has differing impacts on two Manchester clubs
Juan Mata settled Wednesday's Manchester derby to ease the pressure on United manager Jose Mourinho but prolong the frustration for City boss Pep Guardiola.
United playmaker Mata scored the only goal of a tight contest at Old Trafford to send United through to the EFL Cup quarter-finals.
Victory was the perfect tonic for Mourinho after Sunday's 4-0 hammering at Chelsea but rival Guardiola is now in unfamiliar territory having gone six games without a win for the first time in his career.
Mourinho, who was also criticised after a goalless stalemate at Liverpool last week, said: "I couldn't be prouder than I am to be Man Utd manager. The only way I know is to fight - to work and fight.
"I'm happy the players did everything and they deserved to win. In the last week everything went against us but we are professionals.
"This is not the Champions League final, it is just the League Cup last 16, but it is against City and it is after a big defeat, so it was very important for us."
After a lacklustre first half, United upped the tempo early in the second half and struck the post before Mata found the net with 54 minutes gone. United will now go on to play West Ham next month for a place in the last four.
City were the cup holders but there was a feeling victory might matter more to United following their indifferent start to the campaign. That appeared to be reflected in the teamsheets with Mourinho making just four changes compared to Guardiola's nine.
Even so, City's failure to win yet again has further damaged the aura they built up by winning their first 10 games of the campaign.
Reflecting on the winless sequence, Guardiola said: "Sometimes it happens in football the manager doesn't win. Sometimes you win, sometimes not.
"It is the first time (for me), okay, but hopefully it does not happen again in my career. We have had these six times but we are going to change it as soon as possible."
City failed to register a shot on target during the 90 minutes.
But Guardiola said: "Congratulations to United, they made a good performance. We had no normal chances. We had chances on the counter-attack but with no last pass.
"But we controlled their long balls with their tall guys and I am happy for the performance of the players who don't normally play. So, no regrets. We will improve."
Guardiola also revealed captain Vincent Kompany, still easing back into action after a lengthy lay-off, was taken off at half-time after saying he felt "tired".