Formula One:Brawn taken aback by Rosberg pole

Mercedes team chief Ross Brawn admitted he was taken by surprise on Saturday when Nico Rosberg grabbed pole position for Sunday's Bahrain Grand Prix - and sealed the Silver Arrows' first back-to-back qualifying success since the mid-1950's.

The 27-year-old German outpaced compatriot and current championship leader, defending triple world champion Sebastian Vettel of Red Bull, to clock the fastest time.

"To be honest, I didn't see it coming," said the Briton, a seasoned veteran of Formula One success having steered another German Michael Schumacher to all seven of his drivers' world titles with Benetton and then Ferrari.

"We didn't have things right. It's cooler than we expected today and that's a concern for tomorrow. It was tight and in the last run, he didn't push that hard, but he still put together a very good lap.

"Nico gradually got there as he worked at it and although we had some car issues today, it's a great job."

'Car issues' was an understatement for the problems that hit luckless Briton Lewis Hamilton.

The 2008 champion, who had enjoyed two successive podiums for the team in his opening three races as well as grabbing pole for last weekend's Chinese Grand Prix, suffered a major car failure at the end of the morning's final free practice session.

His Mercedes appeared to collapse when the left rear suspension failed and he had to nurse it back to the garage. The repairs included the installation of a new gearbox for which he was handed a mandatory five-places grid penalty. After clocking the fourth best time in qualifying, to take ninth on the grid, he was then taken away for a mandatory random anti-doping test.

Rosberg said he expects Sunday's race to be "much more difficult" than Saturday's qualifying session.

"We will not be as quick as we were in qualifying compared to everyone else," said Rosberg, whose previous pole spot came in last year's China Grand Prix which he went on to win for his sole success yet.

"It will be much more difficult. It was not clear before qualifying who had the quickest car, especially over one lap.

"The team worked well last night to improve the car as we were struggling. It is a fantastic result, great for tomorrow, but tomorrow will be a tough day with rear tyre degradation."

He added that while Mercedes had made progress since struggling in free practice on Friday, he was unsure if it will translate into giving him a car capable of winning the race.

"Yesterday, we were in a difficult situation, we were not where we wanted to be or where we were in the last couple of races," he said.

"To be the absolute quickest today is great and is down to having done really good work last night and this morning. For the race, the competition will be tough. It's difficult to say if we have enough pace to win but we'll try and I'm looking forward to starting first."