Erik ten Hag has claimed his game plan for the Manchester derby was going "how we wanted" before United limped to a 3-0 defeat to rivals City on Sunday.
The Red Devils started brightly in the opening ten minutes at Old Trafford but then fell behind to Erling Haaland's penalty midway through the first half as the gap in quality began to show.
United may have gone into half-time on level terms had Scott McTominay not been denied by City goalkeeper Ederson but instead the deficit grew when Haaland grabbed his second in the 49th minute.
The performance from Ten Hag's side dropped off during the second half as City asserted their dominance with a third from Phil Foden late on.
Although he would not give an opinion on the decision from referee Paul Tierney, Ten Hag pointed towards the awarding of a penalty for Rasmus Hojlund's pull on Rodri as the turning point in the match.
The Dutchman said: "First half, we played very well. The game plan went on how we wanted. We defended very good. They almost didn't create - one big save from Andre in that start. We had two or three breaks, we had to take benefit from it.
"We have to take more from it, but the penalty is changing the game. I don't have a comment on it. I don't have a comment.
"Game plan, first half we were were very disciplined and you can see how successful you can be. The second goal, we made the mistake, we made the wrong decision to go up to the goalkeeper in the wrong moment. And we did not recover quick. They got into the game and power in the midfield, they could switch the game and put players in wrong positions. But it started with us. Then they outplay us."
Ten Hag's substitutions also drew criticism as Sofyan Amrabat was withdrawn at half-time and replaced by summer signing Mason Mount before City took more control on the game.
READ THE LATEST MAN UTD NEWS, TRANSFER RUMOURS & GOSSIP
This article was originally published on 90min as Erik ten Hag explains how Man Utd game plan unravelled in derby defeat.