SAKHIR, Bahrain (AP):Nico Rosberg kept the upper hand on his Mercedes teammate Lewis Hamilton by setting the fastest time in yesterday’s practice sessions for the Bahrain Grand Prix, as Formula One’s top team dominated again.Rosberg, who won the season-opening race in Australia and the final three races of last season, set a best time of 1 minute, 31.001 seconds at the Sakhir circuit, a quarter of a second faster than Hamilton.”We were very quick on one lap and also on the longer runs, so I’m really looking forward to qualifying and the race,” Rosberg said.Mercedes was in a league of its own, with third-place Jenson Button of McLaren 1.3 seconds off Rosberg’s time. That was an encouraging performance for McLaren, which has been on a slow development path with engine partner Honda since last season.Ferrari, which appears to be Mercedes’ main challenger this season, was further off the pace. Kimi Raikkonen was fifth, followed in sixth by Sebastian Vettel, who was forced to park the car trackside due to a loose nut on his left rear wheel late in the evening session.Ferrari believes it has better pace over longer runs than the brief bursts in practice and qualifying, and also demonstrated much better acceleration from the standing start than Mercedes in the season opener, yet Vettel recognised his rival’s strength.THE BENCHMARK”Mercedes are the benchmark. They have looked really competitive this afternoon and this evening, but hopefully, we can be a bit closer,” Vettel said. “The car feels all right. There’s bits and bobs we can improve.”Max Verstappen was fourth fastest for Toro Rosso, the Red Bull pair Daniil Kvyat and Daniel Ricciardo was seventh and ninth, respectively, and Williams drivers Valtteri Bottas and Felipe Massa eight and 10th. Williams is set to use a redesigned front wing today.The heavily criticised rolling elimination format for qualifying will be used again today. The format resulted in an embarrassing anticlimax in the final Q3 session in Melbourne as teams sought to preserve tires rather than attempt to improve times. The teams met on race day in Australia and resolved to revert to last year’s qualifying system but could not unanimously agree at the F1 Commission on how to alter it, so rolling elimination remains.Renault driver Kevin Magnussen is facing a grid penalty after failing to stop and have his car weighed when directed to do so during yesterday’s evening practice session.