Takuma Sato marked his return to Formula 1 with a bang – as he staked his claim to a race seat with Scuderia Toro Rosso in 2009 by impressively topping the first day of winter testing in Barcelona, even if the Faenza-based squad insisted that little could be read into the final pecking order.

With all teams bar Toyota and 17 drivers in action around the Circuit de Catalunya, lap times were clouded somewhat by the fact that some ran their 2008 cars whilst others wheeled out an interim 2009 version.

STR stuck to their 2008 mount and Sato made good use of it to head the timing screens, just over four tenths of a second faster than the second-placed driver, his fellow auditionee for a seat at the Red Bull 'junior' outfit, GP2 Series front-runner Sébastien Buemi. The duo covered respectively 121 and 117 laps of the Montmeló track as they helped the team to assess the slick tyres that will make a welcome return to the top flight in 2009.

Both drivers completed their low-downforce runs on Bridgestone's softer-compound rubber without committing any mistakes and turning in consistent lap times, and whilst Buemi will remain in the car all day on Tuesday, Sato will hand over at lunchtime to 2008 incumbent Sébastien Bourdais.

Buemi ended up just over a tenth of a second clear of third-placed Alex Wurz in the Honda, with GP2 front-runners and F1 aspirants Bruno Senna and Lucas di Grassi some way further down the order in 15th and 17th positions respectively as they duel it out for potentially the second berth at the Brackley-based concern next year. Senna completed fewer laps of the pair, but wound up the quicker by more than a second in their internecine battle to impress.

Experienced hand Wurz, for his part, spent his time evaluating various aerodynamic components for next season and running the Bridgestone Potenza slick tyres. The Austrian will hand over to regular driver Jenson Button on Tuesday for the remainder of the test.

“The view from the cockpit is just so much nicer with slick tyres on the car!” the former Benetton and Williams ace joked. “As a driver I prefer the driving style with slicks, so I am happy that the change has finally come, even if it is too late for me to race with them.

“My focus for today was on gathering information with the tyres whilst running various 2009 downforce levels. We have come away with good answers and a clear direction, so I am pleased with the work that we achieved.

“It was nice to see the two young guys in action with Honda today. Both understood the car very quickly, but how they develop from here with a full day in the car will be important.”