Jul.11 (GMM) Toro Rosso engineers are working hard to get Sebastien Bourdais up to pace with his on-form young teammate Sebastian Vettel.

Multiple Champ Car title winner and F1 rookie Bourdais, on a single-year contract in 2008, has struggled notably since the Faenza based team received the latest car from supplier Red Bull Technology.

"He has a problem with the nervous rear when he's turning in," team boss Franz Tost told Germany's Auto Motor und Sport.

Vettel admits: "Bourdais prefers a car more with understeer. To me it makes no difference whether it is understeering or oversteering."

So is Bourdais, 29, now fighting for his place at STR in 2009? "Simply he has to find the accelerator pedal," is how Tost puts it.

In the Frenchman's favour is the current state of the driver market for next year. Unlike in the last few years, no drivers have been spectacular in GP2 this season, and Toro Rosso is not going to be keen on installing an all-new driver lineup, should Vettel move as expected to Red Bull.