Jenson Button said he had had a "pretty awful race" after finishing 11th for BAR-Honda at the Australian Grand Prix.
Button, who dropped from eighth to 11th at the start, said: "It was pretty bad. The start was my fault and then at first I thought we really slow.
"But once I got past Jacques Villeneuve I was lapping in one minute 26secs, which was pretty good."
Team boss Nick Fry said: "The car performance wasn't there and we have to work on that."
Button's team-mate Takuma Sato followed the Englishman home in 12th place.
BAR brought both men into the pits on the last lap so they could benefit from a rule that allows teams to change their engines without penalty if they do not finish a race.
A new rule for this season demands engines must be used for two entire race weekends.
"The car ran reliably but clearly this wasn't the way we wanted to start the season and we have a lot of work to do to get back up to where we need to be," Button said.