Pep Guardiola complained that his players were "a little bit sloppy" but the Manchester City manager was delighted to rubberstamp a Champions League quarter-final place.
The Spaniard saw his side duke out a goalless draw with Sporting CP, sealing a 5-0 aggregate win after the thrashing in Lisbon three weeks ago.
City probed for a goal to satisfy the packed house at the Etihad Stadium, but they could not make a breakthrough, Gabriel Jesus having a strike disallowed for offside after a VAR check and a late flurry coming to nothing.
Given City's huge lead from the first leg, there was always a likelihood this would end in anti-climax, but the hosts at least avoided an uncomfortable night.
Guardiola said: "The first half was better than the second one.
"I think after the disallowed goal, we were a little bit not active, didn't make movements and it's not easy because after this result the second half I think it was already over.
"We waited for counter-attacks and it was a little bit not good. But I understand it, that games in these situations it is difficult to handle it.
"The first half was much better, we were more aggressive and created chances.
"We should have played the second half like we played the last four or five minutes. We didn't do it; that's why it was a little bit sloppy, the second half."
City have now reached the last eight of the Champions League in each of the past five seasons, the only English side to do so each time over this period.
Guardiola gave Champions League debuts to three players: starter CJ Egan-Riley and substitutes James McAtee and Luke Mbete.
Egan-Riley did well at right-back, with Guardiola saying of the 19-year-old academy product: "CJ played like he is. He's not exceptional in anything, but he doesn't make mistakes and so always as a defender that's so important."
A highlight of the night for City supporters was a late cameo for veteran third-choice goalkeeper Scott Carson, as the 36-year-old replaced Ederson for the closing 17 minutes.
Carson, rarely given a look-in at first-team level, had to make one big save to keep City on terms, boosting his cult hero status at the club.
It was his second appearance in the Champions League, 16 years and 338 days after his debut for Liverpool against Juventus in April 2005 when he was 19 years old. This made it the largest gap between appearances in the competition's history.
"We are delighted. Scott is very important for us always behind the scenes," Guardiola said of the former England international.
"His chemistry with Ederson and Zack [Steffen] is fundamental in the locker room. People listen to him a lot when he talks. For a game like this it was so important and he made the biggest save so we didnt lose the game."
Guardiola played down the prospect of possibly facing a rival Premier League club in the quarter-finals, saying: "We'll prepare well and next Friday we're going to see the draw and we are going to prepare.
"It's an honour to be there. Important teams are already out so we'll see next week what happens."