Bruno Senna has revealed that Bernie Ecclestone has advised him not to 'commit himself too tightly' in 2009, lest the opportunity arises for him to make his grand prix debut after all - with suggestions it is Rubens Barrichello's position that could be the most under threat.

Last year's GP2 Series runner-up, Senna was indeed considered likely to make his F1 bow this year with Brawn GP, in the seat that ultimately went the way of his more experienced countryman. That left him with no racing programme in place for the campaign ahead, though he has since agreed terms to compete for leading sportscar squad Oreca in the Le Mans Series and iconic Le Mans 24 Hours.

However, it was confirmed by Mercedes late last week that despite in-depth discussions right up until the night before it made its official driver announcement, the 25-year-old had turned down an offer to race for the three-pointed star, Brawn GP's engine-supplier, in the DTM European touring car series [see separate story - click here].

That has been viewed as an indication that the nephew of the late, great three-time world champion Ayrton Senna is eager not to make himself unavailable should an opening emerge in the top flight during the course of the current season, as well as the fact that Mercedes-Benz Motorsport Vice-President Norbert Haug was reportedly unable to guarantee him an F1 drive in 2010.

"Formula 1 is the goal, which is subordinate to everything else this year," Senna told German news agency SID. "Bernie told me that I should not too tightly commit myself [outside of F1].

Aside from compatriot Barrichello, other drivers believed to be coming under pressure to perform include Force India veteran Giancarlo Fisichella, Williams' Japanese ace Kazuki Nakajima, Scuderia Toro Rosso sophomore and former multiple Champ Car king S?bastien Bourdais and the underperforming Nelsinho Piquet at Renault.