Daniel Suarez says he did not feel at home during his time competing with Joe Gibbs Racing in the NASCAR Cup Series.
The 26-year-old Mexican lost his drive to 2017 champion Martin Truex Jr for next year, although he is understood to be in the running to land a seat with Stewart-Haas Racing.
The 2016 Xfinity Series champion was rushed into the #19 JGR Cup seat following the surprise retirement of Carl Edwards at the end of that season, and he says it never felt like he had a "winning team" once he made the step up.
"Joe Gibbs Racing was really good for me," Suarez told Autosport. "We ran together for four and a half years, we won races, we won a championship and a lot of good things, but when we got in the Cup Series, things were not the same.
"I never felt like I had everything to win. Lots of people changes, but I've never had a winning team.
"JGR is a great team but I felt it was not my home, I felt it was not the place to be to win races and maybe, one day, the championship.
"There was something inside me that said I needed a change."
JGR's original plan for Suarez was for him to remain in the second-tier series for another season after he won the Xfinity title.
"When I went to the Cup Series it was very fast," he said. "The team was not thinking about putting me in the Cup car that year, but Carl Edwards was retiring.
"Two months after I got in, the crew chief left, the car chief left, engineers left, a lot of things changed and I did not like that.
"This year, again, they changed many things and it was not for the better, I was not in agreement with all the changes.
"I talked a lot, I'm a very direct person in what I see and what I say.
"Thank God, there were a lot of really good opportunities out of Joe Gibbs and I felt like I had to take a step forward in my career."
Suarez said he and his team saw little progress from a rocky start in his rookie season and never developed the consistency needed to become a contender for wins.
"I didn't feel that in two years we improved, I felt worse," he said. "By the end of the first year we were much better than a year later.
"We had good races, but we were not constant. Today we were running in the top five and tomorrow in the top 20, it was very inconsistent."
Suarez is confident his new Cup ride will provide more opportunities for success.
'What I can say is we will be in the NASCAR Cup in a good team," he said.
"We're working on the last few details, but we'll be fine. I hope to be in a position to win races next year."