Following its traditional summer break Formula One action resumed today at Spa-Francorchamps, with Mercedes’ Nico Rosberg setting the early weekend pace in the first practice session ahead of the Belgian Grand Prix.

The championship leader ended the opening session with a best lap of 1:51.577, outpacing team-mate Lewis Hamilton by 0.097s.

Mercedes-powered cars dominated proceedings, with just the Ferraris of Fernando Alonso and Kimi Raikkonen and the Red Bull of Daniel Ricciardo figuring in a top 10 otherwise solely populated by cars using Mercedes power units.

Alonso finished the session in third place, just two tenths down on Rosberg’s table–topping time. He was followed by the McLaren-Mercedes of Jenson Button, with Spa specialist Räikkönen, a four-time Belgian Grand Prix winner, slotting into fourth place.

Sergio Pérez posted a useful fifth-fastest time for Force India, while Kevin Magnussen was sixth, though the Dane was over half a second down on McLaren team-mate Button.

Nico Hulkenberg was eighth fastest in the sister Force India car ahead of Ricciardo. The Australian’s team-mate Sebastian Vettel had a troubled session. The German reported gearbox problems, ran wide at Pouhon and then was forced to retire from the session with exhaust failure. The team later reported that he would miss FP2 as a result of the issues.

Valtteri Bottas was the only Williams driver to finish inside the top 10, seven tenths quicker than team-­mate Felipe Massa.

Further back, Alexander Rossi drove the session for Marussia, at the end of a confusing 24 hours for the team. Yesterday, the team reported that the American racer would drive for the whole weekend in place of regular racer Max Chilton due to “contractual issues” with the British driver, a decision confirmed by the race stewards.

On Friday morning, however, the team, again with the permission of race stewards, reversed its decision and reinstated Chilton to his race seat, with Rossi confined to an FP1 outing. The US driver finished the session in 20th place, 5.6s down on Rosberg.

Behind him, making his first grand prix weekend appearance was three-time Le Mans winner and 2012 World Endurance champion Andre Lotterer.

The German, who races for Audi Sport Team Joest in the WEC, is racing this weekend for Caterham, replacing regular driver Kamui Kobayashi. He finished the session in 21st place ahead of team-mate Marcus Ericsson.

2014 Belgian Grand Prix – Free Practice 1 Times
1 Nico Rosberg Mercedes 1:51.577 25
2 Lewis Hamilton Mercedes 1:51.674 0.097 24
3 Fernando Alonso Ferrari 1:51.805 0.228 16
4 Jenson Button McLaren 1:52.404 0.827 21
5 Kimi Räikkönen Ferrari 1:52.818 1.241 17
6 Sergio Perez Force India 1:52.903 1.326 24
7 Kevin Magnussen McLaren 1:52.922 1.345 23
8 Nico Hulkenberg Force India 1:52.937 1.360 22
9 Daniel Ricciardo Red Bull Racing 1:52.972 1.395 19
10 Valtteri Bottas Williams 1:53.172 1.595 20
11 Sebastian Vettel Red Bull Racing 1:53.369 1.792 11
12 Daniil Kvyat Toro Rosso 1:53.594 2.017 21
13 Romain Grosjean Lotus 1:53.597 2.020 20
14 Adrian Sutil Sauber 1:53.703 2.126 14
15 Felipe Massa Williams 1:53.968 2.391 20
16 Jean-Eric Vergne Toro Rosso 1:54.189 2.612 20
17 Giedo van der Garde Sauber 1:54.335 2.758 16
18 Pastor Maldonado Lotus 1:55.336 3.759 21
19 Jules Bianchi Marussia 1:55.782 4.205 19
20 Alexander Rossi Marussia 1:57.232 5.655 20
21 Andre Lotterer Caterham 1:57.886 6.309 24
22 Marcus Ericsson Caterham 1:57.977 6.400 24