Daniil Kvyat has conceded Toro Rosso's form early in the 2015 Formula 1 season was tough to deal with after his move over to Red Bull.
Following his switch from Toro Rosso, Kvyat struggled to find his feet as he scored just five points from the first five races, not helped by Red Bull's woes with the Renault engine.
Following the Spanish Grand Prix, Kvyat's form was questioned by Red Bull advisor Helmut Marko, particularly following the strong start to the year by Toro Rosso rookies Max Verstappen and Carlos Sainz Jr.
Kvyat then performed strongly from the Monaco GP onwards, going on to outscore team-mate Daniel Ricciardo.
Asked whether he felt he had been promoted a year too soon, Kvyat told Autosport: "You can't have any of those regrets.
"It's a coincidence Toro Rosso built an extremely strong car that matched us quite a lot.
"It was another thing that wasn't easy to accept for me at the beginning of the year.
"But I had to put these kind of thoughts away, and in the end, as a group, we scored more points than them.
"It's fair enough to compare because the cars are very similar."
Ultimately, Kvyat has no regrets on his switch, adding: "It was easy to mess up the whole thing in the beginning, or even the middle of the season.
"But I think I still managed to come out of it in quite a good way, so I don't think it was too early.
"This kind of thing makes you stronger, you can't pick your perfect moments.
"You just have to adapt yourself and that's what I had to do. In the end I'm happy with how my move from STR to Red Bull went."