Japanese GP: Ross Brawn adamant Mercedes isn't dropping back

The Mercedes team principal was adamant when the exhaust was first raced in the Singapore GP that there was still more pace to come from the car.

But at Suzuka, Michael Schumacher and Nico Rosberg could manage only 13th and 15th fastest in qualifying respectively.

Brawn admitted that there is still work to do with the package, but that the team continues to struggle on high-speed circuits like Suzuka.

"It [the exhaust] is working as we expected it to - we're just not at our most competitive here," he said when asked by AUTOSPORT if he was disappointed with the performance of the upgraded Mercedes.

"There is still some more optimisation that we can find.

"This sort of track falls in line with Barcelona and one or two other tracks where we have struggled to be as competitive as we would like."

Rosberg, who will start 13th thanks to penalties for Schumacher and Force India driver Nico Hulkenberg, believes that the improvement made by Mercedes has been shrouded by the steps made by teams around it.

"Of course, I'm not enthusiastic and happy with where we are at the moment," Rosberg said of the team's qualifying performance.

"Then again, our updates have worked and have improved the car.

"Position-wise, that's not been the case and it seems that other people are also progressing and doing a very good job with development so we haven't been able to close the gap and have just equalled their development pace."

Rosberg is also optimistic that the team can continue to improve, with further parts scheduled to be introduced in the next five races.

"We have parts coming in the next few weeks in Korea and the races after that.

"It's a steep learning curve for us to understand where we went wrong and we are understanding a lot.

"I'm optimistic that the next few races are going to be progress.

"We know our weaknesses and it's something we can improve in the next month, especially looking to next year."