Bahrain Grand Prix: Nico Rosberg fastest in opening practice session

The Silver Arrows continue to hold an edge over the rest of the field

Mercedes driver Nico Rosberg (Getty)

Nico Rosberg completed a practice double in Bahrain on Friday as he bids to stamp his authority on the new Formula One season.

Rosberg, winner of the season-opening Australian Grand Prix a fortnight ago, finished the day-and-night sessions at the Sakhir Circuit comfortably ahead of his Mercedes team-mate Lewis Hamilton.

The Silver Arrows appear to hold an ominous advantage over the rest of the field with McLaren's Jenson Button - the next-best placed driver - 1.2 seconds slower than Rosberg's best lap of one minute and 31.001 seconds. Indeed Rosberg's fastest time was comfortably faster than Hamilton's pole lap here last year.

Sebastian Vettel, the driver widely expected to take the challenge to Rosberg and Hamilton in 2016, endured a troubled day, ending the opening session in 11th before parking his Ferrari later in the day.

"Something has happened," Vettel, sixth fastest in the second session said. "I stopped the car, I lost drive." A loose rear wheel nut was later diagnosed to be the problem.

The German's Ferrari was then winched away on a tractor as he watched the remainder of the session trackside with the marshals.

Nico Rosberg turbo locks a wheel on track during practice (Getty)

The rain which paid an unexpected visit to the Gulf Kingdom on Thursday was nowhere to be seen for both practice sessions, but the relatively cool 21-degree air temperature, and overcast skies, meant the conditions were more representative of those expected for Sunday's floodlit race.

Fernando Alonso, a winner here on three occasions, was forced to observe the action as a spectator in the McLaren garage after he was sidelined with a rib injury sustained in his high-speed Melbourne crash.

His participation at the next round in China remains in doubt, but his late withdrawal has paved the way for Stoffel Vandoorne, the highly-rated McLaren reserve driver, to take his grand prix bow this weekend.

The 24-year-old Belgian, last year's GP2 champion, hastily dropped his Super Formula testing commitments in Japan to catch an overnight flight to Bahrain.

He arrived here early on Friday morning after a 13-hour flight - hardly the ideal preparation for his Formula One debut. After an error in which he ran wide at turn 11, Vandoorne ended the first session in 18th before progressing up the leaderboard later on Friday, posting the 11th-best time. It signalled an encouraging day for McLaren, with Button the best of the rest behind the Mercedes drivers.

Max Verstappen, the ever-impressive 18-year-old, was fourth-quickest for Toro Rosso with Kimi Raikkonen fifth in his Ferrari. Daniil Kvyat, Valtteri Bottas, Daniel Ricciardo and Felipe Massa completed the top 10. Briton's Jolyon Palmer, who impressed on his debut in Melbourne, finished the second session in 18th, 2.6 seconds slower than Rosberg.