Ever the perfectionist, Pep Guardiola was unhappy with his side's defending during their emphatic Premier League victory over Southampton.
Goalkeeper Ederson gave away a penalty as he upended Danny Ings in the first half.
He dispatched from the spot, leaving his manager disappointed with his side's defensive capabilities.
"We did some very good things, the first 20 minutes was excellent and offensively we were very good, but we conceded a lot," Guardiola told 'Sky Sports'.
"The game gave me a good feeling, but at the same time, we didn't defend well, although with 6-1 I am so satisfied. We were lucky to score the fourth goal in the final minute of the first half, because otherwise it would have been complicated after half-time.
"As a team, he [Mark Hughes] demanded a lot, and today we were very clinical, especially at the start, and we had the feeling we would create a lot of chances.
"But when they had the ball in midfield we didn't control the balls, they won all the second balls, we had to defend deeper and were not stable enough - and that's why the fourth goal was so crucial."
The victory takes champions Manchester City two points clear of Liverpool and Chelsea at the top of the Premier League table for their biggest lead of the campaign so far, but Guardiola spelled out how the individual qualities of their opponents could yet stop them in their tracks.
"It's not decisive to be top, it's better to be there than be below but the distance between the teams is two, three or four points, it's nothing," he said. "All three [Manchester City, Liverpool and Chelsea] are incredible, with Arsenal we have seen yesterday how good they were against Liverpool.
"Tottenham, despite having a lot of problems, are still winning games and we know how difficult it is to win at Wolves, and United are always there. It will be a really tough league, but it's important we are stable like last season."