David Coulthard has been warned that he will have to produce the best season of his career if he is to maintain his position in a top team in 2005.
Brundle (left) is under no illusions about Coulthard's prospects
The Scot is to be dropped by McLaren after 2004 to make way for Juan Pablo Montoya and will need new employment.
His manager, Martin Brundle, said: "David will have to drive well all season to give us a chance of finding a competitive seat for 2005.
"He knows only too well what he must do to stand a chance of a top drive."
McLaren announced in November that they had signed Montoya from Williams for 2005, and have yet to confirm who will be his team-mate.
But BBC Sport has learned that McLaren will retain Coulthard's team-mate Kimi Raikkonen to partner Montoya, leaving Coulthard out in the cold after nine years with the team.
Former F1 driver Brundle, speaking to the Sun newspaper, added: "David didn't get the job done in the middle of the season and that was when McLaren started looking around and thinking about Montoya.
"And David got a bit scrambled in the head with qualifying."
Coulthard won the first Grand Prix of 2003 but hit a poor spell that started at the fourth race and lasted for much of the season.
But Brundle, who had a 12-year career in F1, pointed out that Coulthard is a match for Raikkonen when he performs at his best.
"David was very unlucky in Malaysia and Brazil (the second and third races last season) and should have won.
"He had an outstanding end-of-season race in Japan where he was miles quicker than Kimi.
"He blew his doors off on a circuit whch is one of the greatest tests of skill and speed."
Brundle added that Coulthard has "no plans to retire because he wants to continue racing - and winning".