Pep Guardiola acknowledged his substitutions made for a nervous finish after seeing his Manchester City side ease up in a 3-1 win over Leicester City at the Etihad Stadium.
City closed the gap on Premier League leaders Arsenal to three points as Erling Haaland struck twice in the first 25 minutes, after John Stones' fine volley had given the hosts an early lead.
With City cruising against their out-of-form opponents, Guardiola withdrew both goalscorers at the break, with Kevin De Bruyne, Rodri and Jack Grealish following after the interval.
Leicester then threatened an unlikely fightback after Kelechi Iheanacho tapped in for 3-1, with the Nigerian hitting the post late on and James Maddison missing a fine chance.
Asked if Leicester's late onslaught had caused any nerves, Guardiola told Sky Sports: "Of course we were worried.
"It was 3-1 from our mistake and they had the chances with Maddison and Kelechi, so the game was tricky in the last 15 minutes. The first 60 or 65 minutes was good.
"I'd like us to push ourselves better and avoid what happened after 3-0, so we do not suffer, but it happened because of the substitutions. From my experience, when you do that, this happens."
City have won nine successive games as they chase silverware on three fronts, and Guardiola says alterations were necessary in order to preserve his stars' fitness.
"We started really well, with incredible focus, but at the end when you make a lot of substitutions at the same time, you always drop a little bit," he said.
"If the guys from the second half started, it would be the same approach that we had in the beginning. It's just a fact that playing every three days, we have to make a lot of rotations.
"I made just two [changes] in the beginning. When the game was under control, I made the rest."
City turn their attentions to the Champions League on Wednesday, looking to defend a 3-0 first-leg lead when they visit Bayern Munich in an attempt to reach the semi-finals.
Asked by BBC Sport if Bayern had a chance of overturning City's advantage, Guardiola said: "Absolutely, we know that. We have to try our game and think we will win the game.
"We have to defend otherwise they have the rhythm. It's a real tough opponent. We go there to achieve something unique, to reach a semi-final.
"We have to play with the right mentality, be stable in the bad moments and go for it."