Ferrari's Charles Leclerc said Friday there was still work to do despite going quickest in second practice at the Australian Grand Prix ahead of Red Bull's Max Verstappen, with Lewis Hamilton only managing 13th.
Monaco's Leclerc, the early season championship leader, was outpaced by teammate Carlos Sainz in the first 60-minute run at a revamped Albert Park.
But Leclerc fired an ominous warning in the second session with a leading time of 1min 18.978 secs, with reigning world champion Verstappen 0.245secs behind after a late surge. Sainz went third-fastest.
It is early days in the season, with Melbourne only the third race, but a title tussle between Leclerc and Verstappen is forming nicely.
"A bit of a harder Friday for me. FP1 was a bit tricky, I improved quite a bit in FP2, but there is still quite a bit of work to do," said Leclerc, 24, who won the season-opening race in Bahrain.
"I don't think anybody really put the (perfect) lap together today. We need to keep focusing on ourself. Tomorrow is qualifying and hopefully we have a good day. We need to do another step forward, and let's push."
Verstappen, who won in Saudi Arabia two weeks ago, struggled with handling early on, saying on the team radio: "I'm still having the same issues, mate, I can't turn the car" after straightlining into the Turn 10 chicane.
He headed back to the pits after five laps, but returned to ensure Ferrari and Red Bull were again dominant.
"We were lacking a bit of balance, then I think for the final run, we changed the car around a bit and felt a lot happier," said Verstappen.
"A tiny bit off Ferrari but I do think that we can maybe make it a little bit closer."
Veteran Fernando Alonso, who won at Albert Park 16 years ago, was a surprise fourth after a blistering 1:19.537 in his Alpine, ahead of Sergio Perez in the second Red Bull.
Esteban Ocon in the other Alpine secured sixth with 2019 winner Valtteri Bottas a strong seventh for Alfa Romeo, while both the McLarens made the top 10.
But seven-time world champion Hamilton continued to toil, as he did at the opening two races.
His Mercedes has had problems with porpoising – bouncing at high speed – this season after a radical design overhaul and there are no new upgrades for Melbourne.
Both he and teammate George Russell hit trouble. Russell, who finished 11th, slid through Turn 2 and Hamilton bounced onto gravel at Turn 14.
Four-time world champion Sebastian Vettel's return to action after missing Bahrain and Saudi Arabia with Covid also went badly wrong.
After setting some respectable times, the German jumped out of his Aston Martin with 14 minutes of the first practice left as smoke billowed from the back.
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