Ross Brawn insists he is comfortable with the way Mercedes GP's preparations for the new season are going - despite questions being raised about the form of the new W02.
Although Michael Schumacher topped the times on the second day of last week's Jerez test, the new Mercedes GP car has appeared to be struggling to match the long-run pace and consistency of rivals like Red Bull Racing and Ferrari.
The team is hoping, however, that a major aerodynamic upgrade scheduled for the Bahrain Grand Prix will help lift its form - and Brawn himself believes it has done the right thing in focusing only on reliability for now.
"We made a deliberate decision towards the end of last year to have a very 'plain' car for the first tests and a significant upgrade for the first race in Bahrain," he said in an interview published on Mercedes GP's official website.
"With the Pirelli tyres, and the return of KERS, we wanted to make sure that our new car was ready for the first test and this was certainly the correct decision.
"The final features for the Bahrain upgrade were confirmed recently and we are comfortable with the performance step that these developments will bring.
"Our current package includes some compromises, and we know that there is more performance to come from the car. Of course, we don't know where the other teams are, and what they have planned in terms of development. No one will have the full picture until the racing starts in Bahrain."
When asked about specific issues that the team needs to address, Brawn said: "Reliability is our main challenge at the moment.
"Although we have completed the third highest mileage of any team with our new car (a total of 2310km), our level of reliability is not where it needs to be yet.
"It's the normal pre-season process really, checking the components, ensuring that everything works together, with the added challenge of KERS and the new tyres. We have experienced our share of teething problems with the MGP W02 but we have solutions in the pipeline to resolve them."
Brawn has also denied that Schumacher's time-topping lap in Jerez last week was a glory run - although conceded that the car had not been fully fuelled.
"There is little point to wasting precious track time on low-fuel 'glory' runs when there is far more important work to complete," he explained.
"As Michael pointed out in Jerez, it was not a particularly low-fuel run, and we are keeping our heads down and concentrating on our own programme. Only each team knows the truth about its performance during the pre-season period, and knowing all the facts, I am satisfied with our progress over the first two tests."