Phillip Island - Italy's Andrea Iannone clocked the fastest time in practice on Friday ahead of the Australian Moto GP in a fiercely competitive session marred by a heavy crash that left Cal Crutchlow with a fractured ankle.
Suzuki's Iannone, who has never won a top level race, powered to a quickest lap of 1:29.131 at the death after switching to soft tyres, with fellow Italian Danilo Petrucci on a Ducati in second, 0.160 behind.
"Our bike has been working really well, but it's always difficult here so a good effort from the team today," said Iannone.
"But we still have to improve in some areas. Everyone will be giving 110 percent in qualifying, so I will need to give my maximum as well."
Yamaha's Maverick Vinales, who topped the first practice run, was third while Andrea Dovizioso, who suffered for pace 12 months ago at Phillip Island, kept in close contention in fourth.
But newly-crowned world champion Marc Marquez, who has an insurmountable 102-point lead from Dovizioso at the top of the standings, struggled around the demanding circuit in seventh, 0.608 off the pace.
The Spaniard, who won the race last year ahead of Valentino Rossi, took a tumble, hitting the deck on the hard turn 10 during first practice.
He got straight back on his feet, but it wasn't a good omen for a rider who crashed out of the Australian race in 2014 and 2016.
Britain's Crutchlow, the 2016 winner, also had a big fall and was stretchered away holding his right leg before being transferred to Melbourne for treatment.
He ended the day fifth fastest but will not be racing on Sunday after fracturing his ankle.
"The fall left Crutchlow with a bimalleolar fracture and anterior tibia part right ankle fracture, an injury that will require the Honda rider to undergo surgery," MotoGP organisers said.
They added that he had been "ruled him out for the rest of the weekend".
It was a big blow for the Briton who had been hoping to build on his second place in Japan last weekend.
Veteran Rossi, the Australian winner from 2001 to 2005 and again in 2014, could only manage tenth on a dry track after the early rain cleared.
It was disappointing for the Italian, who is pressuring Dovizioso in the sprint towards the season runner-up spot behind Marquez.
While a handful of riders came off their bikes, at least the world's best didn't have to contend with the local wildlife, unlike the Moto3 contenders, with a wallaby hopping across the track in front of one bike at turn 5.
A black swan also took a liking to the picturesque circuit that fronts the ocean, waddling over the tarmac during a lull in proceedings.