Australian Jack Miller was fastest at a chaotic practice session for the season-opening Portuguese MotoGP as Spanish veteran Pol Espargaro was hospitalised after a violent crash.

Miller clocked a best time of 1min 37.709sec on a KTM, setting a new lap record at the Portimao circuit.

“To be honest, I’m as surprised as you guys, especially on the time,” Miller said, per motorsport.com.

“[I’m] not [surprised by] the improvements, but of the time. I wasn’t expecting a 1m37.7s but, hey, I’ll take it.”

Maverick Vinales, of Aprilia, and reigning world champion Francesco Bagnaia, on a Ducati, filled out the top three.

However, the high-speed crash suffered by 31-year-old Espargaro on his KTM Tech3 GASGAS bike caused a long interruption to the session which eventually finished around two hours late.

The Spaniard, who moved to his new team after two disappointing seasons at Honda, lost control of his machine on Turn 10 in the second session and was catapulted off the track.

Espargaro, who rolled into a wall, was treated trackside for around half an hour before being airlifted to hospital by helicopter to Faro for treatment to a back and neck injury.

“He suffered a dorsal and thoracic trauma,” said a statement from championship promoters Dorna.

Espargaro was “conscious” at the time “and was transferred to Faro hospital for further examinations.”

The crash reignited calls from drivers to improve the safety of the track, with a particular focus on the size of the gravel at Portimao.

“It’s four years that we’re asking to change the safety of this track,” Bagnaia said, per The Race.

“The first time we arrived here in the track walk I did with my team, I sent a picture of the gravel to [then-MotoGP safety officer] Franco Uncini, that was too big. And it was the normal form of the gravel, and the size, too.

“Last year, when I took the gravel to the box, everyone was laughing at what I did. And nothing changed until the crash of Diggia. That I think was too late, because already with the crash of [Jorge] Martin [in 2021] was quite easy to understand was a problem.”

Bagnaia said an air fence is needed at the corner where Espargaro crashed, with Marc Marquez calling for the change “tomorrow”.

“Not next year, tomorrow,” he added.

A crash in the dying minutes of the session for six-time MotoGP world champion Marc Marquez on a factory Honda meant the Spaniard, who has undergone four surgeries in recent seasons, was out of the Top 10.

He will have to fight through the first qualifying session for a chance of a spot in the second run on Saturday.

Earlier, the session had also been delayed by technical issues which affected the timing mechanism.

The top 10 in practice on Friday wax completed by Luca Marini, Jorge Martin, Fabio Quartararo, Johann Zarco, Marco Bezzecchi, Aleix Espargaro and Enea Bastiaini.