Nico Rosberg, Mercedes Rule Opening Bahrain Practice

Nico Rosberg clocked the fastest lap ahead of his Mercedes team-mate Lewis Hamilton in Friday's second free practice for this weekend's Bahrain Grand Prix. (Read More in Formula One)

The 30-year-old German produced a best lap of one minute and 31.001 seconds in the floodlit second session at the Bahrain International Circuit to outpace the defending three-time world champion by 0.241 seconds.

The two Mercedes men were more than a second clear of the rest of the field led by Jenson Button in his surprisingly competitive McLaren-Honda, who was third.

Button was still 1.280 seconds slower than Rosberg, but after their dreadful 2015, this was a major step for the team. (Fernando Alonso to Miss Bahrain Grand Prix on Medical Grounds)

Rosberg's continuing success meant he had topped the times in both sessions on Friday and, after winning the season-opening race in Australia, ensured he was in a confident mood as he went into the weekend.

Dutch teenager Max Verstappen was fourth fastest for Red Bull ahead of Ferrari pair, Kimi Raikkonen, the 2007 champion, and four-time champion Sebastian Vettel.

Vettel ended the session watching the action from behind a barrier after a problem with the left rear of his car brought him to a halt at Turn 12.

"The left rear corner was not tight, the nut was not on," said Vettel on the team radio.

Daniil Kvyat was seventh for Red Bull, ahead of Valtteri Bottas of Williams and his Australian team-mate Daniel Ricciardo who was ninth. Felipe Massa was 10th in the second Williams.

On his maiden outing with McLaren Honda, following the enforced withdrawal of two-time champion Fernando Alonso, the team's official reserve driver Stoffel Vandoorne was an impressive 11th.