Jenson Button was critical of Brawn GP's one-lap pace after qualifying just fourth for the Bahrain Grand Prix, suggesting that the team's rivals have not merely caught up with them but have in fact overtaken Formula 1's new boys - and already fearing that the honeymoon may be coming to a sudden end.

Having consummately dominated the opening two grands prix of the 2009 campaign in Australia and Malaysia, a wet race masked Brawn's true pace in China a week ago, but even in the torrential conditions Button was able to take the chequered flag in third position, behind the two runaway Red Bull Racing machines of Sebastian Vettel and Mark Webber.

After qualifying in Sakhir, however, the British star contended that even the rostrum may be out of reach for the former Honda F1 outfit in the desert kingdom, with grip woes in the searing heat seeing the 29-year-old ultimately come up more than six tenths of a second shy of Jarno Trulli's pole position - and running barely any heavier than the front row-sitting Toyota duo [see separate story - click here].

"I'm very surprised," the world championship leader confessed. "It's not the Toyotas so much, it's more our lack of pace. We were aiming for pole position today, but unfortunately it wasn't our best qualifying session of the season and the pace just wasn't there. I didn't have a great lap on my final run in Q3, and we were struggling for grip on the corner exits and locking tyres throughout the session. We struggled, and compared to the whole field we don't have the pace we did in the first few races.

"Our competitors have obviously made advances and caught up quickly, and it's going to be a tough race tomorrow - it's not going to be a walk in the park. At the moment we don't have the pace of the Red Bulls and the Toyotas. We're starting fourth, and fuel-corrected we'll be fourth I think. We're not quick.

"Our pace is good over long runs, but we've shown today that our one-lap pace is not competitive. In Q2 - where we do struggle most on low fuel - we were sixth, I think. Obviously we're a bit quicker with higher fuel, but we're not [running] long; I should think the guys at the front are [pitting] around the same lap as we are.

"Our race pace was good yesterday when we were doing long runs, but the problem is when you're back there in fourth - I might as well say fifth, because these guys (Lewis Hamilton and McLaren-Mercedes) have got KERS - it's quite difficult. We'll do the best job with what we have, though, and if it's hot like this tomorrow and we can get a clean start I think our pace will be good."

Button will be starting two spots ahead of Rubens Barrichello, who blamed traffic on his 'out' lap in Q3 that left him just under two tenths of a second adrift of the sister BGP 001 in the final reckoning, having set an identical lap time to his team-mate on low fuel in Q2.

"Unfortunately qualifying didn't go as well as we planned today," reflected the experienced Brazilian. "I suffered from traffic on my final run in Q3, when I was in the middle of a group who were taking it slowly on their 'out' laps. That was different to my approach, and meant that I couldn't get enough temperature into the tyres which compromised my quick lap. Our competitors are improving, and it will be interesting to see how that affects the race. It's going to be tough, but I am confident that good points are possible tomorrow."

Indeed, an objective of 'points' rather than the podium or even victory is an indication of just how the situation has changed since the start of the campaign only five weeks ago, with Brawn's rivals on the march and - once all are equipped with the split-level diffuser - the Brackley-based concern's initial advantage looking likely to be wiped out altogether. These are worrying times for a team that not so long ago looked to be almost invincible.

"The track and ambient temperatures are incredibly high here today," summarised team principal Ross Brawn, "and we are learning all the time how to make the tyres and chassis work in such extreme conditions. The track has evolved since morning practice, and neither driver was completely happy with the balance of their car.

"However, we were able to make progress through the sessions and have secured decent grid positions for the race tomorrow. The forecast is for slightly cooler weather, which should be beneficial for the performance of the track and car. We will reflect on our qualifying performance overnight, and see what we can learn ahead of the race."