Brawn believes that with this year's competitiveness mirroring last year's strong start in the opening three races, only a good showing in Bahrain, where the team struggled last year, will show what sort of shape it is in.
In 2012, Mercedes followed up its Chinese Grand Prix victory with fifth in qualifying and the race in Bahrain for Nico Rosberg.
"The pleasing thing is we've been to three races this year and we have not been bad," Brawn told AUTOSPORT.
"Bahrain will be the final one of the quartet that will tell us if we have a car that we can get to work at most places.
"We seem to have, but we have to lift the performance another two or three tenths compared to the opposition, and we know it is a moving target."
Brawn said that there were plenty of encouraging indications already that Mercedes had a much better car this year.
"Sector two in China, which is a sort of aero sector, often we were the quickest car there and last year it was one of our weaknesses - so that is pleasing," he said.
"There are some good hints that we have something that we can work with."
Lewis Hamilton, who has two podiums and a pole position to his name already this season, believes Mercedes' current run of form proves that it can be involved in the title fight this year.
Brawn himself agrees that there is a chance of that, and he is hopeful that victories are not far away.
When asked about Hamilton's title prediction, Brawn said: "The opportunity is there. We have two great drivers, and Lewis is not out of touch.
"But we have to step up with the car. We still have to improve, so we can go to a race weekend with a stronger chance of winning.
"We had a smell this weekend [in China], but we were a little bit off the pace because of the balance, and a couple of good drivers and good cars filled that gap.
"But we are getting a smell. And we will do everything in our capacity to chase it."
- Sports & Recreation
- Motor Racing