Nico Rosberg was left to rue an engine issue which limited him to just 45 laps on the final day of the four-day pre-season F1 test at Jerez.
Rosberg had seen Mercedes team-mate Michael Schumacher enjoy two trouble free days of running the new W02 before he reclaimed the car for the final day only to see his planned programme halted by the need to carry out a precautionary engine change after he stopped on track.
Although able to return to action to work on aerodynamic evaluations later in the day, Rosberg admitted it was unfortunate not to have been able to spend more time on track.
"Every lap is beneficial in pre-season testing and the work that we achieved today was good, however the long stoppage was unfortunate,” he said. “It's a steep learning curve and there is a lot of hard work ahead, but with the developments that we have to come, I am confident that we will continue to progress."
Despite the problems encountered over the course of the four days, team boss Ross Brawn insisted the Jerez test had been useful for the team although work remains to improve the reliability of the new car.
"The four days in Jerez have proved to be extremely useful for the team, although the test has not been without its challenges. We had good reliability for the middle two days which allowed us to accumulate a lot of mileage, however there are issues to be resolved so that we can maximise our track time for the remaining two tests.
“Both Michael and Nico continue to feel comfortable in the car and our priorities remain on reliability, developing our understanding of the tyres and the KERS, whilst simultaneously pushing on with the developments still to come."
To view times from day four in Jerez, click HERE