Mercedes Nico Rosberg has set the fastest time in practice for the Australian Formula One grand prix.

Rosberg set the pace around Melbourne’s Albert Park street circuit on Saturday, with Jenson Button’s McLaren 1.4 seconds behind in second and Fernando Alonso third in his Ferrari.

Rosberg’s Mercedes teammate Lewis Hamilton was fourth quickest and Australian Daniel Ricciardo was fifth best in his Red Bull.

The only concern for Mercedes might be a littering fine after Rosberg found a stray component in his hands as he drove – later shown to be a “thermal elbow protector” – tossing it from his car.

Rosberg’s 1:29.375 lap was the fastest this weekend, setting up a keen challenge between the two Mercedes drivers for pole position on Saturday afternoon.

The biggest surprise from Saturday’s final practice session was the absence of world champion Sebastian Vettel from the top of the timesheets, citing acceleration problems through team radio to end 12th.

Intermittent showers and sharper wind added to the challenge facing the drivers as they continue to adapt to their new cars.

Romain Grosjean fought an ongoing battle with his Sauber car, forced back into the pits three times with various problems.

McLaren drivers Kevin Magnussen and Button provided an early highlight by taking off-road trips on the same turn within one minute of each other.

The same corner was causing concern for Hamilton, who twice took excursions at turn nine on hot laps, preventing him climb back to the top of the charts.

Sauber’s Esteban Gutierrez struggled around his first flying lap of the circuit, citing gearbox issues and did not record a time.

Likely cellar-dwellers Caterham’s weekend improved as both drivers were able to chart lap times for the first time, though found themselves well off the pace.