The opening test of the 2010 pre-season last week showed that Toro Rosso is not lagging behind, according to Sebastien Buemi.
At Valencia, the team's continuing Swiss driver gave the first fully Faenza-designed Toro Rosso its track debut.
"While real comparisons are still difficult, we know that we are currently able to compete with Mercedes, Renault and Williams," the 21-year-old told the Swiss newspaper Blick.
"Ferrari, McLaren and Sauber are ahead," Buemi added. "Yes, the Swiss car (Sauber's C29) surprised me. Now only the Red Bull car missing."
After winning the drivers' and constructors' titles (as Brawn) last year, and with Michael Schumacher now at the wheel, some observers expressed surprise that Mercedes GP was off the pace with its new W01 at Valencia.
Team boss Ross Brawn told Bild newspaper: "We are in a reasonable position, and have identified the areas where we can improve."