Mercedes team boss Ross Brawn has conceded that the new MGP W01 wasn't as quick as he had hoped this week during testing at Valencia in Spain.
Michael Schumacher and Nico Rosberg both drove for the Brackley-based outfit – former 2009 F1 title winners Brawn GP – over the three-days. However the team's best lap, a 1 minute 12.438 seconds - set by record-breaking multiple F1 world champion Schumacher - left them only seventh on the combined times.
"On full tanks we didn't look too bad but we are a little bit off the pace," Brawn told BBC Sport
. "The handling and balance of the car is not quite right, but we can fix it for Jerez. We know what the problem is.
"Of course the other teams will be progressing as well. We are not as quick as Ferrari, and Lewis Hamilton looked quick on Tuesday for McLaren, so it looks like we have got a bit of work to do.
"We are cracking exhausts and we have to change those every 150-200 kilometres. It is a problem we can fix but here it is difficult.
"We've got a handling imbalance because we are all learning about these tyres here and we've seen straight away some things we want done on the tyres which we will have done by Jerez."
F1 2010 testing continues next week at Jerez with running commencing on February 10 and concluding on February 13.