Having got out of Q1 in 13th, Perez was the only driver not to be on track at the end of Q2, and missed out on a final flying lap.
When he was called in, he was told he was in fifth and that there were still four minutes of the session remaining.
After a pause, he said to his engineer: "We finished quite early, no?" and his concern proved to be valid as he subsequently found himself bumped down to 12th - and will start the race in 11th due to Carlos Sainz's grid penalty.
"We had a strategy before qualifying with the team," said the Mexican. "And obviously we don't know this place, and we were thinking what was the best programme, and we went this route.
"Obviously after that, it's easier to know that it was the wrong call. Already in Q1 we were a bit lucky to get through because we didn't get our final lap coming back to the pits.
"And then Q2 just finishing the session a little bit too early meant that there was some evolution still on track, and we were in the pits."
He made it clear that he hadn't expected to finish his session with so much time left on the clock.
"I wasn't aware that much that we were going to finish that early," he said.
"But also, we didn't seem to have the ultimate tenth in it today. So we were lacking a bit of pace out there. As I say this is a new place for us, so I wasn't expecting it, but it's how it is."
Perez also stressed that getting temperature into the tyres was a challenge.
"Yeah, it hasn't been straightforward," he said. "I think you saw in qualifying people doing different sorts of programmes. And some people got caught out with it, and we were one of them."
He remains optimistic that he can make progress in the race.
"I think that deg could be potentially really high out there," he said. "So plenty of things to look at tomorrow, and we will see what we are able to come out with.
"I think we should be able to have a lot faster race pace than qualifying pace, so hopefully that will bring us forward tomorrow."
