Nico Rosberg topped the opening practice session of the Belgian Grand Prix weekend by less than 0.1s from Mercedes team-mate Lewis Hamilton on Friday morning. The session remained dry throughout, allowing drivers to attack the Spa-Francorchamps circuit for the first time in the new V6 turbo era. The cars were visibly more difficult to drive than in recent years, with the high-speed left hander at Pouhon catching out a number of drivers who were attempting to carry too much speed in to the corner. Hamilton was among the drivers to leave the track at Pouhon, and did so on two consecutive laps, as he chased down the slim advantage Rosberg had midway through the session. Fernando Alonso was third fastest and 0.228s off Rosberg, although it is not the first time the Ferrari has shown promising pace in FP1 only to struggle later in the weekend. Jenson Button was fourth fastest in the McLaren ahead of Kimi Raikkonen, who was fifth but still a second off the pace of team-mate Alonso. Sergio Perez was sixth, Kevin Magnussen seventh, Nico Hulkenberg eighth and Daniel Ricciardo ninth in the highest-placed Red Bull. Sebastian Vettel was 11th fastest and two seconds off the pace of the lead Mercedes, but was limited to just 11 laps after a problem kept him confined to the garage for the second half of the session. Despite being one of the favourites to challenge Mercedes ahead of the weekend, Williams failed to show much in the way of giant-beating pace in the opening session, with Valtteri Bottas tenth and Felipe Massa down in 15th. Massa looked like he was struggling throughout the lap, with the car sideways in a number of Spa's low and medium speed corners. Bottas finished the session with a 1.595s gap to the top of the timesheets. After learning that he would only be in the car for FP1 rather than the whole of the weekend, as previously announced by Marussia, Alexander Rossi put in a respectable performance with the 20th fastest time behind team-mate Jules Bianchi. However, he will give the car back to Max Chilton for FP2, who has now agreed terms to stay retain his driver for the rest of the weekend. Caterham new boy Andre Lotterer also impressed with a time faster than regular race driver Marcus Ericsson. Lotterer may have been 6.309s off Rosberg, but did well to beat his team-mate by just under a tenth on his first outing in the car. Ericsson spun at Turn 1, which will not have helped his chances or the condition of his tyres, but Lotterer did not appear to put a wheel too far wide all session.