McLaren's Formula One leader Lando Norris lapped fastest in first practice for the title-deciding Abu Dhabi Grand Prix on Friday with closest rival Max Verstappen 0.008 of a second slower.
The Briton, who set a best effort of one minute 24.485 seconds around the Yas Marina circuit, was one of only 11 race regulars taking part in a session otherwise handed over to young prospects and development drivers.
Verstappen sounded concerned over the radio with his car's handling on a slippery surface in unrepresentative afternoon heat, with Sunday's race running into the night under floodlights.
"There might be something broken on the car," he reported.
McLaren's Oscar Piastri, the third title contender but 16 points behind Norris, watched from a pitwall seat as 26-year-old Mexican IndyCar driver and F1 reserve Pato O'Ward lapped in the Australian's car.
"There's some guy that has taken my seat," joked McLaren boss Zak Brown.
Under Formula One rules each regular driver must make way in two Friday first practice sessions per season for rookies or drivers who have started no more than two grands prix.
Ferrari's Charles Leclerc was third fastest with his younger brother Arthur 16th in Lewis Hamilton's car.
The Monegasque siblings made history at the track last year when they became the first brothers to take part in a practice session as teammates but the older Leclerc sounded less happy this time.
"The car just feels like it has zero grip. It is unbelievable," he said.
Mercedes had both their race regulars Kimi Antonelli and George Russell on track, fourth and sixth respectively.
Sauber's Nico Hulkenberg, gearing up for his 250th start, was fifth fastest.
Toyota-backed Japanese driver Ryo Hirakawa, 31, was the fastest of the non-race drivers in 11th for Haas, and ahead of Racing Bulls' Isack Hadjar in 12th.
Arvid Lindblad, who will take Hadjar's seat next season when the Frenchman moves to Red Bull as Verstappen's teammate, was 15th in Yuki Tsunoda's Red Bull in his third practice session of the campaign.
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