MELBOURNE, Australia - Nico Rosberg maintained Mercedes' dominance with the fastest time in practice ahead of Saturday qualifying for the Formula One season opener in Australia.The German dashed around Melbourne's Albert Park street circuit in a best lap of 1min29.375 seconds, 1.391sec ahead of McLaren's Jenson Button.TOP FORMRosberg's team mate Lewis Hamilton, who was fastest in Friday's practice, was fourth quickest (1min30.919), behind Fernando Alonso of Ferrari.Hamilton and Rosberg have been tipped to fight it out in Sunday's race, given Mercedes' superior pre-season testing and adjustment to rule changes, which include a fuel limit.Rosberg had an eventful session. At one stage he was seen throwing something out of his cockpit while driving and then reported to his team that his tyres were "finished".Four-time World champion Sebastian Vettel struggled in his Red Bull with the 12th best lap time and complained that his car could not accelerate and he was unhappy with the Renault engine.Frenchman Romain Grosjean's fraught weekend continued when he reported his Lotus Renault engine was misfiring, to which he added with exasperation "unbelievable".In another fascinating exchange overheard on the team radio, Kimi Raikkonen told his Ferrari garage: "You have to be more precise in telling me the switches."German Adrian Sutil also advised his Sauber team, "the car is all over the place," to which his engineer instructed "pit then".The session finished with Pastor Maldonado's Lotus Renault car stopping on the track, forcing him to return to pit lane on foot.Qualifying for grid positions in Sunday's race was scheduled for later Saturday with the possibility of rain.Final practice times on Saturday for 2014 Australian GP1. Nico Rosberg (GER) Mercedes 1min 29.375sec 2. Jenson Button (GBR) McLaren Mercedes 1:30.766 3. Fernando Alonso (ESP) Ferrari 1:30.876 4. Lewis Hamilton (GBR) Mercedes 1:30.919 5. Daniel Ricciardo (AUS) Red Bull Racing 1:30.970 6. Nico Hulkenberg (GER) Force India 1:30.978 7. Kimi Raikkonen (FIN) Ferrari 1:31.156 8. Kevin Magnussen (DEN) McLaren Mercedes 1:31.251 9. Sergio Perez (MEX) Force India 1:31.665 10. Felipe Massa (BRA) Williams 1:31.723 11. Daniil Kvyat (RUS) Toro Rosso 1:31.925 12. Sebastian Vettel (GER) Red Bull Racing 1:32.255 13. Jean-Eric Vergne (FRA) Toro Rosso 1:32.417 14. Jules Bianchi (FRA) Marussia 1:34.184 15. Adrian Sutil (GER) Sauber 1:34.188 16. Kamui Kobayashi (JPN) Caterham 1:34.413 17. Max Chilton (GBR) Marussia 1:34.717 18. Pastor Maldonado (VEN) Lotus 1:34.754 19. Marcus Ericsson (SWE) Caterham 1:36.159 20. Valtteri Bottas (FIN) Williams 21. Esteban Gutierrez (MEX) Sauber 22. Romain Grosjean (FRA) LotusSecond practiceFirst practiceStay with Wheels24 for the first 2014 F1 race in Australia this weekend.