On Michael Carrick's debut as manager, United defeated Manchester City 2-0 thanks to goals from Bryan Mbeumo and Patrick Dorgu.
Guardiola said afterwards: "The better team won. They were better. When a team is better you have to accept it. They had the energy we didn't have, so congratulations.
"They had the chances at the end and of course the goals we conceded were poorly. We didn't control but in general we can talk about this action or that action. We have the duty to analyse the game in general and they were better.
"They started really strong, we lost one or two balls. The crowd is normal, because it is a derby. In many years they have been behind them and also with the new manager it is normal these kind of things in the game.
"We never made a threat or a cross or a movement to try and win that. It is also part of the energy, win or lose it is about what we do with the ball as well, not just without.
"It is not about one player.
"It is about how we grow up as a team. I have the feeling we have done very good things so far. To be better you may have to take a step back. The season is a long way and you have to continue to analyse."
Asked if Diogo Dalot should have been sent off for a nasty challenge on Jeremy Doku, he added: "You could say that, you could say that red card, different game.
"Many, many situations happen. It is easy for me to come here and say it should be a red card. It is not about that, we will not grow up if that is the argument to win or lose a game. To do you have to do better and we didn't today."