Giedo van der Garde is adamant there is still "some scope" for Caterham to improve their CT03.
Introducing their first major upgrade at last Sunday's Spanish Grand Prix, Caterham showed signs of progress in their battle with Marussia.
While the Malaysian team had initially been lagging behind, in Barcelona van der Garde qualified ahead of both Marussias while on the Sunday his team-mate Charles Pic beat their rival backmarkers.
"There is still some scope, absolutely," the Dutchman told ESPNF1.
"So we have to see what we have to do and how we can fix it because at the moment it is not there completely.
"I think to be honest we will make another step during the season and hopefully it will be as good as this one.
"But still I think we have to optimise this and then we will have more potential and we will be faster, but the team is pushing hard so that is why I'm very happy with it."
This is a sentiment echoed by his team-mate Pic, who says there is still some way to go with the CT03.
"What I know is that for sure the car is not optimised now," he said. "But then after, I don't know if we optimise it what it will give."