Jenson Button has admitted that Brawn no longer has the performance advantage that it enjoyed in the first two races of the season after qualifying fourth for the Bahrain Grand Prix.
Although in previous races the Brawns have qualified on a heavier fuel load than the Red Bulls and Toyotas in Q3, Button believes that the front-runners will all start the race on similar weights.
"We've struggled compared to the whole field and we don't have the pace we had in the first few races," Button told the BBC
's F1 coverage. "It's going to be a tough race tomorrow -- it's not a walk in the park.
"At the moment, we don't have the pace of the Red Bulls and the Toyota. Our race pace was good yesterday when we were doing long runs,but the problem is when you are in fourth place it's difficult. We'll do the best job with what we have. If it's hot like this tomorrow, our pace will be good."
Button believes that on single-lap pace the Brawn has slipped behind some of its rivals. Despite the car's strength on long runs, he is not certain that he and teammate Rubens Barrichello will be able to get to the front in tomorrow's grand prix.
"We're starting fourth and fuel-corrected we'll be fourth," he said. "We're not quick. Our pace is good over long runs, but our one lap pace is not competitive.
"In Q2, where we do struggle more with low fuel, we were sixth. We were a little bit quicker with high fuel, but we're not long and I think that the guys at the front are [pitting] around the same lap that we are."