Jose Mourinho admitted Manchester United made life hard for themselves against Northampton Town in the EFL Cup - but praised his players for their second-half display in the 3-1 victory at Sixfields.
The four-time winners of the competition went ahead in the third-round tie when Michael Carrick scored his first goal for the club in 556 days, only for the hosts to equalise through Alex Revell's penalty.
However, United took the lead for a second time when Ander Herrera's low drive found the net in the 68th minute.
Substitute Marcus Rashford capitalised on an air shot from goalkeeper Adam Smith to put the game beyond Northampton, clinching United a place in the last 16, where they will entertain neighbours Manchester City.
"Teams from lower divisions, when they reach this level of the competition and they get the big boys, it's a great occasion. They raise the level of their game," Mourinho told MUTV after ending a run of three straight defeats in all competitions.
"It was difficult because we arrived at half-time level at 1-1. At half-time, if we were winning two or 3-0 like we should and could have been, the game would be over.
"The reality was, though, that at the end of the first half the game was still open at 1-1.
"We coped well mentally with that risky situation. In the second half, we didn't stop until we scored."
The draw for the fourth round gives Mourinho's squad the chance to avenge the 2-1 Premier League loss they suffered against rivals City at Old Trafford earlier this month.
"I think it's good for us. We can show again what we want to do," Herrera - who scored his first goal of the season against Northampton - told MUTV.
"We were very disappointed, because it was in front of our fans against city opponents. Now we have another chance to play against them - I'm sure it will be different."