Rosberg tops final practice in Melbourne ahead of F.One qualifying
Mercedes driver Niko Rosberg of Germany powers out of his garage during the third practice session of the Formula One Australian Grand Prix, in Melbourne, on March 15, 2014 - by Paul Crock
The German dashed around Melbourne's Albert Park street circuit in a best lap of one minute 29.375 seconds, 1.391sec ahead McLaren's Jenson Button.
Rosberg's teammate Lewis Hamilton, who was fastest in Friday's practice, was fourth quickest (1:30.919), 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.