Erik ten Hag has thanked Pep Guardiola and Manchester City "for the lesson" they handed his Manchester United side at the Etihad on Sunday.
United were beaten 6-3 in the derby, only salvaging some respect with two late Anthony Martial goals having been 6-1 down in the closing stages.
It was the fourth defeat in nine games for Ten Hag as United manager and the second time they've been beaten heavily this season, having also lost 4-0 at Brentford in August.
Ten Hag believes the defeat to City is a "reality check" for his team and will help them in the long run, but he plans to continue setting his team up to try and hurt the opposition.
"That’s what you always do, you take respect of the opponent but we still stick to our philosophy, our rules, our principles," he said.
"In tactics sometimes, to surprise opponents, you have to bring something different to your game, and we will do that also in the future.
"But we can get a lot of confidence about this theory, when you beat Arsenal, you beat Liverpool, now we get a reality check with Man City, we know we have to step up. So thank you for the lesson, Pep and City, we will take that, and we have to understand we have to do things much better.
"I know when you’re in a process it will not go only upside, you will have setbacks. We beat the No. 1 in the league, we beat Liveprool, on Sunday we had a bad at the office and we got beat, in this moment on that day City was better, we have to accept that, but we can’t accept our performance, that was unacceptable."