Michael Schumacher is hoping the late arrival of his new Mercedes would pay off after doing nearly two race distances in last year's car on the second afternoon of Formula One testing on Wednesday.
Despite that, and despite setting a quickest lap that was meaningless on a day when rivals were trying out their new cars, the German still played down his title chances.
The seven-times world champion pounded out 132 laps, with a best time of one minute 18.561 seconds, to gather tyre data on the new Pirelli rubber.
Australian Mark Webber was quickest of those in the new machines, putting in 97 laps for champions Red Bull with a best time of 1:19.184 ahead of compatriot Daniel Ricciardo in the Toro Rosso.
World champion Sebastian Vettel takes over in the Red Bull on Thursday, a day that should see more locals at the Jerez circuit with Spain's Fernando Alonso in the Ferrari after Brazilian Felipe Massa did the first two days.
Lewis Hamilton will take over from Jenson Button in the McLaren, the only one of the new crop of cars not to have a stepped nose.
Mercedes have decided not to run their 2012 car until the second pre-season test in Barcelona later this month to give them as much development time as possible.
"It (bringing the car out late) maybe is an important factor because we have worked longer on our car," the 43-year-old Schumacher told reporters afterwards in a huddle at the back of the Mercedes garage.
"As I said before, I don't think we can realistically achieve a championship car from where we started last year.
"We have to build our way there. I'm confident we can do that, in future, but let's take it step by step," added the German, who has not been on the podium since he began his comeback in 2010.
Schumacher said reliability was the main focus and Mercedes hoped to have learnt from the past.
"Our programme is done in a way that we believe in it," he added.
"I'm around to fight for the championship. Whether we can or cannot do it, that is something that will be proven this year, or whenever."