Nico Rosberg set the fastest time in the first practice session for the Bahrain Grand Prix, holding a margin of 0.505s over his Mercedes team-mate Lewis Hamilton in second.
The Australian Grand Prix winner was marginally slower than Hamilton in the first sector but a whopping 0.385s quicker in sector two and 0.165s faster in the final sector. Impressively, both Mercedes drivers set their quickest times during 12-lap stints on the soft tyre.
But first practice in Bahrain is rarely a useful guide to true performance as it is one of just two sessions held during daylight hours during the weekend, with both qualifying and the race taking place under floodlights after sunset. As a result, Ferrari will not be too concerned by Kimi Raikkonen's 1.834s gap to Rosberg, while team-mate Sebastian Vettel was eleventh fastest after opting only to use the slower medium-compound tyre during the 90 minute session. Both Ferraris completed relatively short run plans, with just 30 laps between them but no obvious issues.
The session started with most of the focus on the McLaren garage as Stoffel Vandoorne, standing in for the injured Fernando Alonso, kicked off his debut grand prix weekend in the No.47 MP4-31. Vandoorne finished the session with 25 laps to his name, split over soft and medium tyres, and set the 18th fastest time. By comparison, team-mate Jenson Button was 0.952s faster and 14th quickest overall.
The order behind the Mercedes drivers and Raikkonen resembled that of the opening round in Australia, with Red Bull fourth and fifth, albeit over two seconds off the pace of Rosberg. Nico Hulkenberg managed to finish sixth ahead of the two Toro Rossos of Carlos Sainz and Max Verstappen, while Romain Grosjean hauled his Haas into the top ten with an impressive lap on soft tyres to go ninth ahead of Felipe Massa, who was the only Williams representative in the top ten.
At the bottom of the timesheets, Alfonso Celis made his grand prix weekend debut for Force India as part of his season-long deal to feature in seven free practice sessions this year. His time of 1:37.287 was 2.686s off team-mate Nico Hulkenberg and 21st overall, ahead of Manor's Rio Haryanto. Sergio Perez will be back in the Force India for FP2.