George Russell made an immediate impact with Mercedes, clocking the quickest time in Friday's first practice session ahead of the Sakhir Grand Prix.
Russell has stepped in to replace absent world champion Lewis Hamilton in Bahrain after his fellow Briton tested positive for COVID-19 earlier this week.
The 22-year-old's fastest lap was 54.546 seconds, putting him ahead of Red Bull pair Max Verstappen and Alex Albon, who were second and third respectively.
Russell's fellow Mercedes driver Valtteri Bottas was fourth quickest, 0.322secs behind his temporary team-mate.
This race will be staged on a different, shorter track configuration to the one used for the Bahrain Grand Prix last Sunday, a race Hamilton won.
Mercedes team boss Toto Wolff acknowledged it was a promising start for Russell but did not want to get carried away.
"P1 was a good session for him," Wolff told reporters.
"We need to calm everybody down - it was a first practice session on a really short track. But he delivered a really solid job in what we expect from him on a single lap.
"The long runs were difficult with our car and difficult to establish a benchmark, because [Bottas] broke his car early on and it was difficult for him to stop it properly."
Russell was loaned to Mercedes from Williams, who have promoted reserve driver Jack Aitken to their team for the penultimate round of the 2020 F1 season.