MANAMA, Bahrain - Mercedes F1 team chief Ross Brawn hs admitted he was surprised on Saturday (April 20, 2013) when Nico Rosberg grabbed pole position for Sunday's Bahrain Grand Prix then sealed the Silver Arrows' first back-to-back qualifying success since the mid-1950's.The 27-year-old German out-paced compatriot, championship leader and defending triple World champion Sebastian Vettel of Red Bull, to clock the fastest time.VERY GOOD LAPBrawn, a veteran of Formula 1 success having steered Michael Schumacher to all seven of his Drivers' World titles with Benetton and then Ferrari, said: "To be honest, I didn't see it coming. We didn't have things right. 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 was 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 earning pole for the 2013 Chinese GP a week earlier, had a major car failure at the end of the morning's final free practice.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-place 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 expected Sunday's race to be "much more difficult" than Saturday's qualifying session.Rosberg, whose previous pole spot came in 2012's Chinese GP which he won, said before the Bahrain GP: "We will not be as quick as we were in qualifying compared to everyone else.”He added that while Mercedes had made progress since struggling in free practice on Friday, he was unsure if it would translate into giving him a car capable of winning the race."We were in a difficult situation, we were not where we wanted to be or where we were in the last couple of races. To be the absolute quickest today is great and is down to having done really good work last night and this morning." Stay with Wheels24 for the 2013 Formula 1 season – fresh reports every day.