Germany's Nico Rosberg registered the fastest time in his Mercedes in Saturday morning's pre-season testing session at Bahrain's Sakhir circuit. Rosberg managed to go a second faster than his teammate Lewis Hamilton a day earlier, outpacing Jenson Button in a Mclaren-Mercedes and Kimi Raikkonen in a Ferrari. Brazilian Felipe Nasr, a new test driver with the Williams team, took to the wheel for the first time and was fourth-quickest. A final pre-season testing session will take place in Bahrain next Thursday, February 27, before the first race of the season, the Australian Grand Prix in Melbourne, on March 16. Morning testing times 1. Nico Rosberg (GER/Mercedes-AMG) 1min 33.283sec, 2. Jenson Button (GBR/McLaren-Mercedes) 1:34.957, 3. Kimi Räikkönen (FIN/Ferrari) 1:36.718, 4. Felipe Nasr (BRA/Williams-Mercedes) 1:39.036, 5. Sergio Pérez (MEX/Force India-Mercedes) 1:39.258, 6. Daniel Ricciardo (AUS/Red Bull-Renault) 1:39.837, 7. Jean-Eric Vergne (FRA/Toro Rosso-Renault) 1:41.784, 8. Pastor Maldonado (VEN/Lotus-Renault) 1:41.880, 9. Marcus Ericsson (SWE/Caterham-Renault) 1:45.094 Source: AFP