Nico Rosberg topped the second practice session at the Italian Grand Prix after Mercedes rival Lewis Hamilton was hamstrung by an electronic issue for the first half of the session. Rosberg's session appeared to run smoothly as he notched up 41 laps and clocked a 1:26.225 during his early run on the softer medium tyres. Hamilton had to wait nearly an hour for his Mercedes could be fired up after some sensors were changed, limiting him to just 16 laps and a fastest time 0.061s off Rosberg. In the grand scheme of the championship it may only be a minor bump in the road for Hamilton's title chances, but with a 29-point gap to Rosberg in the championship and limited time to find a set-up for Monza's unique layout it will have been felt in the cockpit. Ferrari did the best it could to keep its loyal Tifosi happy, with Kimi Raikkonen just 0.106s off the lead Mercedes and Fernando Alonso 0.340s adrift in fourth. However, it may just be low-fuel showboating in front of the home fans as Raikkonen said on Thursday that Ferrari's power-deficit will be felt in the race on Sunday. Alonso's session finished in the garage with his car surrounded by mechanics, suggesting a late issue with his F14 T. Valtteri Bottas hinted at Williams' potential with the fifth fastest time and 0.533s off thetop, with Jenson Button close behind in the McLaren. Sebastian Vettel was seventh fastest and the highest-placed Renault-powered car, with Kevin Magnussen, Felipe Massa and Daniel Ricciardo rounding out the top ten. Riccardo's time may have been better than first practice, but radio traffic with the pit wall suggested his car still had some minor issues hanging over from the morning. Romain Grosjean was the only driver to have a serious off-road experience, when his Lotus skittered through the gravel at the first Lesmo. On the following lap he missed his braking point into Turn 1 – a common occurrence for several drivers – and only managed the 20th fastest time behind both Marussias. In general the Lotus looked like an untameable beast throughout the afternoon session, with Maldonado also struggling to keep his car on the track, suggesting a tough Sunday awaits for the Enstone team.