Pep Guardiola says Manchester City's 2-0 derby defeat at Old Trafford was the result of his side's lack of energy against a "better" Manchester United.
But Guardiola was aggrieved that Diogo Dalot escaped being sent off for his early challenge on Jeremy Doku.
in his first game in charge after replacing Ruben Amorim.
Goals from Bryan Mbeumo and Patrick Dorgu ensured victory, while United also had three goals disallowed due to offside and hit the frame of the goal twice.
City only managed one shot on target throughout the 90 minutes.
"The better team won," said Guardiola. "They had energy we didn't have. Congratulations to them.
"They had the chances at the end with crosses. We know they are a transitional team, but in general, they were better.
"They start really strong, that's normal.
"We never made a threat, crosses or movement, but that's part of the energy."
Dalot was only shown a yellow card and avoided a sending-off for what former Premier League referee Mike Dean said should have "100 per cent" resulted in a red card.
VAR ruled that the challenge lacked excessive force and therefore the initial caution sufficed.
"He should be sent off, it's a red card since the game. But it will be poor as a manager, I've never been that, if you analyse that, to win or lose a game," said Guardiola.
"I said to Michael and all the players right now here, they deserve that change. It's a red card - definitely. But that will not make us grow up. The new players knew exactly what they had to do, but it's what it is.
"I could say that [the red would have changed the game] and blame. We will not grow up, we will not move forward. But what happened is not a surprise at all for me, but it's not happened in the past.
"When I arrived here, one action, it happened with these referees in Chelsea, in Man City, Chelsea-Gundogan with [N'golo Kante].
"So now I start to realise, it's not about that. Because with that, we grow up, always talking. We have to look at ourselves, honestly. So, what happened in the situation? We should differently, maybe, but who knows.
"There are a lot of teams that win with ten against 11, and I get the feeling with the game that we played, maybe we'll have no win. If the players have excuses for that reason, we'll be in trouble in the future. We have to look at ourselves, and today it's simple."
