Pep Guardiola conceded the game was "over" when Manchester City were reduced to 10 men in the 4-0 Champions League defeat to his former club Barcelona.
The LaLiga champions are five points clear at the top of Group C thanks to a Lionel Messi hat-trick and a solo goal from Neymar that added insult to injury for ragged opponents a minute from time.
City asked questions of their hosts after Messi's 17th-minute opener at Camp Nou, but Claudio Bravo's botched 53rd-minute clearance and subsequent handball to prevent a Luis Suarez goal left them with a mountain to climb.
"At that level it's hard, but until 10 against 11 the game was open and we competed against a very good team with huge personality," visiting manager Guardiola told BT Sport after a painful outing at the ground where he made his name.
"We created enough chance to score goals. After [the red card] the game was over.
"Of course [Bravo] is disappointed because he is a huge professional, but it is part of the game."
Bravo's error is particularly damning for Guardiola, given the Chile international's arrival from Barca heralded the departure of England goalkeeper and fans' favourite Joe Hart to Torino.
But the former Bayern Munich boss recognised an increasing trend of individual mistakes that have stained a run of four matches without a win in all competitions for the Premier League leaders.
"It seems every game there is something like that - own goals, missed penalties and things. We have to change the dynamic," the Spaniard added.
"I asked my players to play with responsibility and we did it.
"We were there, we were in the game. We were pressing, we had the possession and we made the chances. We did it, but we didn't take the chances and you have to do that to win the game."
Guardiola, who left top scorer Sergio Aguero on the bench, added: "We knew from the beginning that it would be a tough group.
"Now we have to recover and think about Southampton [in the Premier League on Sunday]. After we are going to see what happens next."