Piastri topped Qualifying 2 on Saturday in Miami with a 1:26.269s lap on his first run in the segment.
It was a time he was unable to match, let alone beat, in the final segment as he slipped from provisional pole to the second row, behind Max Verstappen, Lando Norris, and Kimi Antonelli.
“This afternoon was nothing to do with luck,” Piastri admitted.
“It was just not the level of execution I needed to have in Q3.
“It’s never a great qualifying session when your best lap is the first lap of Q2, so there was quite a bit left on the table.”
Piastri’s best Q3 effort was more than a tenth off his Q2 time.
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Had he replicated his earlier effort, the championship leader would have finished second behind Verstappen.
The Dutchman found four-tenths in Q3 while Norris improved by two-tenths and Antonelli four-tenths.
“Both laps of Q3 I struggle in Turn 1; I lost pretty much two-tenths in Turn 1,” Piastri explained.
“My first lap of Q3 I kind of gained it back a bit through the rest of Sector 1 and then fell away in the middle.
“The last one, I eventually recovered some of it at the end. It wasn’t enough.
“So nothing to do with preparation, it was just execution of the driving.
“I think after the lap in Q2 I just never quite got back into the same rhythm and that was kind of the difference at the end,” he added.
“Some things to look at for sure, but I know exactly where it went wrong, which is frustrating.”
McLaren headed into Qualifying as favourites for pole position, with the squad looking poised to claim a front-row lockout midway through the hour.
But, not for the first time in 2025, a stunning lap from Verstappen coincided with both Piastri and Norris failing to deliver the full potential of their machine on a single lap.
“There’s definitely some things within our car that we want to try and address, and driving it right on the limit is one of them,” Piastri said.
“This weekend it has had enough pace to be on pole, it’s just that I’ve not done as good a job as I should have.
“It’s always been tight, that gap’s always been close, and potentially our advantage has been a little bit more on Sundays.
“But I think our picture of where we stand has always been that, if we make mistakes, we’re going to be beaten, and that’s been true for me.”
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