George Russell recorded the fastest time on Friday during the first free practice for the Grand Prix of Sakhir.
The Briton, who replaces Lewis Hamilton infected with the corona virus at Mercedes, kept Max Verstappen, who finished second, behind him.
Russell, who normally drives for Williams but has a contract with Mercedes, was almost two tenths faster than Verstappen with 54.546 seconds (54.722).
He also immediately trumped Hamilton's teammate Valtteri Bottas, who had to settle for fourth place at more than three tenths behind.
Alexander Albon completed the top three behind Russell and Verstappen and was within three tenths of the lead.
Verstappen's teammate at Red Bull Racing spun one more time in the opening phase of the practice session, but he managed to keep his car out of the guardrail.
The drivers will drive at the Bahrain International Circuit in Bahrain, just like last week, but for the Grand Prix of Sakhir the track has been shortened considerably.
The drivers cover 2 kilometers less and for the second time in Formula 1 history they take less than a minute to complete a lap.
Grosjean absent this weekend
Romain Grosjean will not be there this weekend either.
The Frenchman van Haas survived a terrifying crash last week.
He is replaced by Pietro Fittipaldi, who finished nineteenth in the first practice.
Only Jack Aitkin, who takes Russell's place at Williams, was slower.
Following the Grosjean crash, security measures have been taken at the site where the incident took place.
Additional tire stacks have been placed there.
Grosjean visited that place on Thursday and thanked the people who helped him on the track.
The Sakhir Grand Prix continues on Friday with the second free practice (6.30 p.m. Dutch time), followed by the third free practice (4 p.m.) and the qualifying session (7 p.m.) on Saturday and the race (6.10 p.m.) on Sunday.
This race has never been on the Formula 1 calendar.
See also: Five questions about GP Sakhir: 'Without Hamilton, Verstappen has a big chance'