SPIELBERG, Austria - A fast car and aggressive approach were vital to Mercedes for overtaking Williams in the 2014 Austrian GP, team mates Nico Rosberg and Lewis Hamilton said.They started third and ninth respectively behind an all-Williams front row but took the lead early and fought off the competition to take their sixth 1-2 in eight races.POWER PROBLEMS Rosberg said: "I thank the team for the great car and a perfect strategy. We chose the aggressive way to pit earlier and to overtook Williams - that worked out quite well."We had to look after our brakes, which was a big job for the whole race, and it too worked out perfectly for me. I can be confident before the next GP at Silverstone."Mercedes saw its winning streak halted by Red Bull in the 2014 Canadian GP two weeks earlier as both drivers suffered power problems and this was a major concern in Austria.Rosberg said: "It wasn't the easiest of races, trying to manage certain things that were a bit on the limit on the car."Mercedes executive director Toto Wolff said: "The race was all about management; managing the brakes and looking after the power unit to make sure we didn't have any repeat ofproblems we had in Canada."'IT'S FRUSTRATING'Still, Mercedes' has a 158-point lead over Red Bull in the Constructors' championship. Hamilton lost almost two seconds to Rosberg in the pit stops at the Red Bull Ring.Hamilton said: "It is frustrating when you lose time because you're constantly doing everything you can to gain a tenth here, a tenth there, so when you lose quite a chunk - two seconds over two pit stops - it's tough."I hope we won't have those problems in future."Stay with Wheels24 for the 2014 F1 season – fresh reports every day.