ART Grand Prix driver Nyck de Vries admits he lost sleep over Luca Ghiotto's Formula 2 Barcelona feature race pace, before a U-turn in form to win the sprint race.
De Vries believes Ghiotto was "35 seconds quicker, that's almost a second a lap" on Saturday, as the Italian fought from the back of the grid to finish fourth and one spot ahead of de Vries.
"It's almost a second a lap [Ghiotto was faster], if you start analysing from that point it's a long evening I can tell you that, my sleep wasn't great," de Vries told Autosport after winning Sunday's sprint race.
"You have to keep the faith and today proved there is no magic, anyone can do the job. I'm happy and proud of that."
The 22-year-old, who has replaced Williams Formula 1 driver George Russell at ART - added that the team "didn't turn the world upside down" in terms of set-up changes for Sunday.
De Vries passed early leader Anthoine Hubert and streaked to a comfortable victory for the team's first win since Russell won in Abu Dhabi to seal the F2 title last year.
"This category is so difficult and you have to be so precise," de Vries added.
"We didn't turn the world upside down, just little changes and little changes make one big change.
"You always have to keep the faith and even if one day looks bad, things can turn around for the next day. I'm especially relieved for that.
"I always trusted in the team and our potential together. I'm very happy and proud to show we can turn things around in the weekend."
Ex-McLaren junior driver De Vries is third in the championship, 30 points off Nicholas Latifi who has won three of the six races this season.
De Vries has yet to finish outside the top seven so far this season.
Ghiotto was at the back of the grid after a second problem of the season at the start of the race dropped him down the pack.
He was then hit by Dorian Boccolacci, which moved him to the back of the field, and he would later recover to fourth.
Ghiotto said he was "afraid" of the pace he showed after Saturday's race.
After the sprint race on Sunday, Ghiotto said: "The team is doing a great job, everybody in the paddock is trying to understand why we are so quick.
"The others did a better race today than yesterday and If I had a better start it may have been easier to move forward.
"But after yesterday we still have to be happy with the weekend."