Brawn GP drivers Jenson Button and Rubens Barrichello have revealed concerns about their car's one-lap pace, after they were outpaced by the Toyotas of Jarno Trulli and Timo Glock as well as Sebastian Vettel's Red Bull in qualifying for the Bahrain Grand Prix.
World championship leader Button, who will start tomorrow's race from fourth on the grid, admitted that while the Brawn-Mercedes was still the best package over long-runs, he had no answer to his rivals when his car is running light.
"Our balance wasn't that great on low fuel, it was a little bit better on heavy fuel as we normally find with this car," said the Briton. "But we don't have the pace and with this heat we are just struggling quite a bit to try and get a balance.
"Our pace yesterday on longer runs was very good, but we just can't get a lap out of it and we've lost out compared to our competitors.
"Yesterday we were quick and today we are not so quick.
"I wouldn't put our position on the grid down to our fuel load, I don't think we are running heavy, I think we are maybe a little bit light.
"We haven't got the pace, we are slower than the Toyotas and I think also the Red Bulls, over one lap," he added.
"But I think on the long runs we do have some pace so we have just got to hope that we can get some clear circuit time tomorrow in the race and we can make the difference there."
Barrichello agreed with his team-mate and explained that he believed that other teams may have caught Brawn GP - which dominated the first two races - with aggressive development programmes since Malaysia.
"We didn't have any improvements for the last two races, and apparently people did improve here and there," said the Brazilian. "For me, I was very surprised to see Red Bulls [fast] in Shanghai, I was expecting Toyota to go well.
"This time the surprise is [Lewis] Hamilton with the pace. We cannot forget that this track is probably more in favour of the KERS than the other three, but it's a bad surprise this time"
Button admitted that starting just one place ahead of Hamilton's KERS-equipped McLaren is an area of concern for him at the start.
He is worried that the world champion could beat him off the line and then hold him up with slow race-pace until the first pitstops.
"My biggest issue is having Lewis alongside me because he has got KERS off the start," said Button. "I don't think his pace in the race will be as good as the other cars in front of me so that's one of the biggest issues.
"I would hope that Fernando Alonso can't get us, because it is about seven or eight metres effect - the KERS – so they shouldn't be alongside me into Turn 1. That's more Rubens's problem than mine.
"So Turn 1 is going to be interesting and we have got to get through it cleanly. We have just got to hope that we are one lap longer than some of the guys in front, and if we are then we can make the difference there."