Haas development driver Santino Ferrucci admits it was hard leaving GP3 in the middle of the season, but reckons moving up to Formula 2 was "the best decision" for his career.
Ferrucci became officially affiliated with Haas in 2016, which was his first year in GP3.
While he finished that campaign 12th overall for the DAMS squad with a podium finish to his name, the start to his sophomore season was not a successful one.
Picking up three points from the first three rounds, Ferrucci decided to step up to F2 from the Hungaroring round onwards, a decision he claims both DAMS and his bosses at Haas supported.
"I will say [it was] the longest week of my life to go through that, mentally tiring as well," Ferrucci, who joined Trident in F2, said after testing the Haas F1 car at Hungary this week.
"It came down to fighting chances at that point, my team boss in GP3 fully supported me because of the technical difficulties we’d been having throughout the season.
"He was more or less making the decision for me at that point and I can’t thank him enough.
"I had to go to Gunther [Steiner, Haas team boss] and talk to him about it, we had a bunch of meetings at Silverstone.
"We thought [moving to F2] would be the best decision moving forward for the next year, two years, and the best thing to prepare me for the F1 car."
Points on "crazy" F2 debut
Ferrucci took ninth in his first-ever F2 race, matching his team Trident's best feature race result of the season.
"Crazy, to say the least," Ferrucci said of his F2 debut weekend. "The GP3 car is amazing to drive, in the high-speed corners it moves a lot and you really feel it.
"The F2 car, everything happens a lot faster, the carbon brakes are a lot different. Even the tyres are completely different.
"In GP3, the tyres stay for a lap or two, the F2 car you start the lap with understeer and you finish it drifting!
"To hang on like that in qualifying was crazy, and to only get three or four push laps before we went into qualifying.
"Then changing [tyre] compounds again made it incredibly difficult but I think the team did a fantastic job preparing me and I can’t thank them enough."
For the rest of the season, Ferrucci's target is to stay in the top 10 in the F2 running order.
"If we can stay in the top 10 or around that area," he said. "I’d be more than happy to have a couple of [high starting positions from] reversed grids and see what we can do."
Additional reporting by Jamie Klein