The Australian finished seventh at Circuit de Barcelona-Catalunya on Sunday while team-mate Lando Norris pushed race-winner Max Verstappen to the chequered flag after starting from pole.
Piastri’s race was heavily impacted by a lack of single lap pace on Saturday, and while there were positives to take out of the race, he admits it was a new experience.
“I would say it’s the first weekend where it’s been such a consistent struggle,” Piastri revealed.
“In some weekends last year, the race was difficult but qualifying was not bad.
“This weekend, it’s just been a struggle the whole way through, even through practice. It’s just not been happening,” he added.
“Obviously just need to understand why it’s been the case; tried a fair few different things setup side.
“I’ve just not had much confidence in the car, which is really the first time I’ve had that in my F1 career.”
Though unable to match Norris in qualifying, which heavily influenced the outcome of his race, Piastri stopped short of branding the weekend the toughest he’s experienced in F1.
“I think some other weekends, especially in some of the other races last year, Sundays were tougher,” he reasoned.
“Here, the race, especially the second half, wasn’t too bad. I think it was just a general lack of pace.
“From a tyre management point of view, it was probably not a bad result, but when you don’t have the pace to begin with, it makes it very difficult.”
Piastri worked on car set-up and his own approach on track in an effort to get on top of the issue, though came away without a clear understanding of what was going wrong.
There are, however, indicators of areas to examine more closely now the weekend has concluded.
“Some hints and potential ideas,” he said when asked if he understood what happened to make the event so difficult.
“I think the magnitude of is… Yeah, doesn’t make 100 percent sense at the moment.
“Just need to try and understand why it’s been such a big struggle this weekend from the first lap.
“Friday, it’s been difficult. It’s not really gotten much better through the weekend.
“We’ve tried a lot, both with the car and with myself,” he added.
“Some of the corners I would say are explainable, others haven’t.
“Some of the corners I felt I’ve driven them well have been worse than the corners where I know I’ve messed them up.
“When you’re having qualifying laps like that, it’s doesn’t fill you with much confidence.
“So, just need to understand why that was the case this weekend.”
In the race itself, Piastri did move forward from ninth to seventh, with Pierre Gasly a big influence on his progress.
The Alpine driver was a cork in the bottle for the McLaren, finally clearing him on Lap 34 after which Piastri’s race began to improve.
“I think the second half of the race was maybe a bit more positive,” he explained.
“Obviously, there was some optimism that if we could get through the Alpines quickly, maybe be in the fight with Mercedes and Ferrari, but ultimately didn’t get through Gasly quick enough,” he added.
“Then, I think after that, the pace was certainly a bit better towards the end of the race.”
Crossing the line seventh, Piastri added another six points to McLaren’s constructors’ championship tally.
However, both Red Bull Racing and Ferrari enjoyed double-points-paying finishes too, meaning McLaren left Spain with a healthy 25 points, but having lost ground to the two teams ahead of it in the constructors’ championship.
F1 is in action again at the Austrian Grand Prix next week, opening practice for which begins at 20:30 AEST on Friday.