George Russell made an emphatic statement of intent on Friday when, in his first practice outing with Mercedes, he topped the times ahead of Max Verstappen at the Sakhir Grand Prix. The 22-year-old Briton, 'on loan' from Williams as stand-in for coronavirus victim seven-time champion Lewis Hamilton, clocked a fastest lap in 54.546 seconds to outpace Red Bull's Dutchman by 0.176 seconds. London-born Thai driver Alex Albon was third fastest in the second Red Bull as Valtteri Bottas, in the other Mercedes, laboured to match their pace on the high-speed short lap 'outer loop' track at the Bahrain International Circuit.
Bottas was three-tenths of a second adrift of his new team-mate - just the sort of instant embarrassment the Finn wanted to avoid - on a day when Russell complained of discomforts with his seat after dropping a shoe size to fit into Hamilton's cockpit.
Russell, in only his second season with Williams, has never qualified in the top ten or scored a point, but has impressed many observers with his pace after graduating from the Mercedes junior programme.
Daniil Kvyat was fifth ahead of his Alpha Tauri team-mate Pierre Gasly, Esteban Ocon of Renault and four-time champion Sebastian Vettel of Ferrari.
Daniel Ricciardo was ninth in the second Renault and Charles Leclerc was 10th for Ferrari.
After an early foray from Sainz, Ricciardo set the early fastest time for Renault after 15 minutes shortly before Russell began lapping in earnest.
The Australian trimmed his time to 55.8 only to see Bottas move clear in 55.1, the Finn clearly keen to establish his seniority - only to spark a set of improved efforts from his new English team-mate.
Russell duly went P1 after 53 minutes before Verstappen and then Albon and Russell took command, trading laps with some elan, the new Mercedes man clocking 54.546 to go fastest.