P1: Rosberg heads Hamilton

Mercedes picked up where they left off in opening practice at the Belgian Grand Prix on Friday morning, with Nico Rosberg fastest ahead of Lewis Hamilton.

Rosberg, the current World Championship leader, lapped the 7.004km Spa-Francorchamps circuit in a time of 1:51.577s to go 0.097s faster than Hamilton, with the Silver Arrows trading times at the top midway through the 90-minute session.

There was absolutely no surprise in any of this, of course, particularly on a track that places a very definite emphasis on power rather than downforce, although the presence of Fernando Alonso in third was notable - the Spaniard having spent most of Thursday downplaying Ferrari's prospects this weekend.

Alonso ended the session about 0.6s faster than Jenson Button's McLaren, with Kimi Raikkonen - four times a winner at Spa - fifth overall despite his Ferrari suffering an overheating ERS system.

Behind the Finn came Sergio Perez's Force India, with the top ten completed by Kevin Magnussen (McLaren), Nico Hulkenberg (Force India), Daniel Ricciardo (Red Bull) and Valtteri Bottas (Williams).

The presence of the Finn in tenth - not to mention that of team-mate Felipe Massa in 15th - suggests another slow start to a weekend for Williams, who have once again been touted as potentially Mercedes' closest rival this weekend.

It has even been been suggested that Bottas and Massa might challenge the Silver Arrows; what already seems likely, however, is that Red Bull are set for a difficult weekend.

With Ricciardo the fastest Renault-powered runner in ninth, World Champion Sebastian Vettel - who started his nine-race romp to last year's title at Spa last year - was 11th fastest.

Further back, it was difficult not to feel sympathy for Alexander Rossi, who had been looking forward to making his F1 race debut this weekend.

However, Marussia revealed during the session that Max Chilton, who was dropped in favour of the American on Thursday owing to "contractual issues", .

Rossi ended the session 20th overall, about 1.5s slower than team-mate Jules Bianchi.

Caterham were still off Marussia's pace, despite a heavily-revised CT05 car which features a new, and rather less ungainly, nose.

Even so, debutant Andre Lotterer gave team regular Marcus Ericsson something to think about by outpacing the Swede by a tenth of a second.