Aug.7 (GMM) Sebastien Bourdais needs to show some better performances this season before his future at Toro Rosso is secure.

That is the warning of Gerhard Berger, the Faenza based team's co-owner.

Frenchman Bourdais, 29, entered formula one this year after a period of total dominance in the now defunct American open wheeler Champ Car series.

But while his teammate Sebastian Vettel has earned a graduation to the senior Red Bull Racing team for 2009, Bourdais has notably struggled ever since the latest STR3 chassis made its debut.

"What we have seen from him so far has not been too bad," Berger is quoted as saying by the Spanish language magazine 'Grand Prix'.

"Until now he has been in a period of formula one apprenticeship and putting in a couple of good results.

"Bourdais will continue with us in 2009 only if he really now begins to show us his potential," he insisted.

Meanwhile, amid rising speculation that Bruno Senna is in pole position for Vettel's 2009 seat, Berger also gave a boost to the hopes of Sebastien Buemi, who this year is an official Red Bull test driver.

Berger said another youngster, British F3 racer and Spaniard Jaime Alguersuari, is not yet ready for F1.

"It needs to be clear that Alguersuari is still at a very early stage of his development as a driver.

"Of all the Red Bull guys, the only one who could have a chance (for 2009) I think is Buemi," Berger explained.