Mercedes GP will wait until the season-opening Bahrain Grand Prix to bring its definitive 2010 diffuser onto its car, team principal Ross Brawn has revealed.
Although the German car manufacturer team is expected to bring a raft of aerodynamic improvements onto its car during Friday test at Barcelona, the final diffuser package will not be part of it.
When asked by Gazzetta dello Sport when the new diffuser would be fitted to the W01, Brawn said: "At the first grand prix in Bahrain."
Brawn acknowledged that his team's winter preparations were nowhere near as impressive as last season's, when his eponymous team dominated the final Barcelona test.
However, despite having struggled early on with getting front tyre temperatures up to the perfect operating window, he was far from concerned about the early performance.
"We knew those performances [from last year] couldn't be repeated," he said. "We can't yet say whether this car is a winner, but we know it's not bad.
"We've had a few small problems, but in Jerez, despite the bad weather, there have been improvements already, in the sense that the team has made progress in the process of understanding the car and the tyres."
Brawn also welcomed the input that Michael Schumacher has given to the team since his return - although he said it was taking time for the seven-time champion to get himself fully back into the swing of things.
"It's a big help: Michael has always been an excellent reference point for me," said Brawn. "We have two new drivers, but he isn't really new: he is precise, clear, he knows what he wants, and he is very good at feeling the car.
"However, he was on the sidelines for three years and the cars have changed greatly during this time. He has to get into the system of a completely new team and he has got to begin getting to know Rosberg and understand how to work together."
When asked if he felt Schumacher had changed, Brawn said: "No, he still has the fire inside, he is very determined and focused on what he does."