Kevin Magnussen says he is proud of his personal performance in 2018.
Haas, however, had an often difficult 2018 season.
"We are still a young team on a steep learning curve," Magnussen told BT newspaper.
"Perhaps we had a better car than we really expected. We were fighting in a higher weight class than the one we belonged to. But it's a luxury problem that shows how much talent and potential the team has," he said.
Magnussen was initially the standout Haas driver in 2018, but Romain Grosjean eventually fought back and the pair will remain teammates this year.
"Romain came back after a difficult period and it might have seemed like I took a step backwards," said Magnussen. "But that was not the case. He had just returned to his highest level.
"It is clear that with the update, Romain got a car that suited him very well. Overall it was better, but unlike Romain I could drive the old one too.
"In fact I have a hard time understanding that it made such a big difference to Romain."
Magnussen thinks Frenchman Grosjean, who was often criticised in 2018, is arguably his best ever teammate in F1.
"If you look at the whole package - human, chemistry, laptimes and so on - Jenson is the best teammate I've had. But there is no doubt that Romain is faster than Jenson.
"On one lap, Romain is exceptionally fast when it all goes well for him," he said.
Indeed, Grosjean won the overall qualifying battle against Magnussen in 2018.
"It would have meant more to me if I had won it," Magnussen laughed. "Perhaps it means something if the big teams are looking at you, but I'm not advertising myself like that."