Renault team chief Flavio Briatore savaged Heikki Kovalainen's debut for the team after he finished in 10th place at the Australian Grand Prix.
Kovalainen agreed he had produced a poor performance
The Finn, 25, was promoted from test driver to replace Fernando Alonso after the Spaniard's move to McLaren.
"If I say it was good, I'm a complete idiot. It was rubbish," Briatore said.
"We know he is good. Because his race was so bad, it was not him. Maybe it was his brother. We will try to get the real Heikki for the next race."
Kovalainen had been expected to give team-mate Giancarlo Fisichella a serious test, but produced an error-strewn performance, running wide and spinning.
He finished two places out of the points while Fisichella was himself a low-key fifth for the world champion team.
Kovalainen admitted there were few positives from his Grand Prix debut.
"To be honest, there is very little to remember from it and lots to forget," he said.
"I didn't have a great race. There were too many mistakes and my performance just wasn't controlled enough.
"My feeling right now is that the next race cannot get a lot worse."