George Russell finishing fastest in practice for the Sakhir Grand Prix as he deputises for Mercedes lead driver and 2020 world champion Lewis Hamilton who is "in bed" and "not feeling great".
The penultimate round of the season will be the first Formula One race staged in 14 years without Hamilton on track after the seven-time world champion's positive Covid-19 test on Monday.
Indeed, Hamilton's victory, which was also in Bahrain, last weekend might have been the 11th and final of his title-winning year with a mandatory 10-day quarantine period ending next Thursday.
Russell, who is part of the Mercedes young driver programme, has temporarily switched from the Williams team to fill in for his fellow British driver in Bahrain's second grand prix in as many weeks.
The season finale takes place in Abu Dhabi next Sunday. But strict Covid protocols are in place with Yas Island effectively placed on lockdown when the F1 world arrives from Bahrain on Monday evening.
"I am not sure Lewis is going to follow in detail what is happening on track this weekend as he is in bed and not feeling great," said Toto Wolff, the Mercedes team principal.
"He is recovering. The first few days are critical when you have corona, and while he has symptoms, they are pretty mild. Racing becomes a second priority. His priority now is getting healthy."
Hamilton, 35, came into contact with an infected person following a holiday in Dubai in the days before last weekend's race in Bahrain.
It leaves the world champions without their £40 million-a-season driver for one, possibly two races, but Wolff added: "Lewis doesn't need any permission to go to Dubai.
"He rides anything he wants, and jumps out of every airplane he wants, because he knows what is best for him. He is a grown-up man and this was never an issue."
Hamilton's enforced absence provides Russell with the opportunity of a lifetime. A Williams driver by day, Russell has been promoted to a seat in the fastest car in F1 history.
He is yet to score a point in his two seasons in the sport but he will head into Sunday's race among the favourites to win.
The Englishman, 22, finished quickest on a new configuration of the Bahrain International Circuit, lapping the 2.17-mile so-called oval track in 54.5 seconds, 0.176 sec clear of Red Bull's Max Verstappen and an impressive three tenths ahead of team-mate Valtteri Bottas.
Russell, who discovered he could replace Hamilton following a 2am bathroom phone call from Wolff on Tuesday, is a member of Mercedes' young driver academy. He persuaded Wolff to sign him with the help of a PowerPoint presentation when he was still a teenager.
"George is totally relaxed," added Wolff. "He comes across on the radio as chatty and buzzing, but he is very focused, and calm.
"The record he has of winning the GP3 and F2 championships, both in his rookie years, stand out.
"I remember he came to my office when he was 15 or 16 and he was wearing a black suit and a black tie with a PowerPoint presentation as to why Mercedes should support his career.
"He is very mature for his age and his personality is well-suited to jump in the car in such a high-pressure situation. But let us keep both feet on the ground. These cars have not been taken out in anger yet."
A strong performance from Russell would place pressure on Wolff to hire him in 2022 alongside Hamilton. Bottas is already confirmed for next season.
But Wolff concluded: "You cannot call it a shootout (between Russell and Bottas) when it is about one or two races.
"If George does well it is an indication that one day he is going to be in a good car and race for victories and world championships but that is far away.
"Where we are in 2022 is not going to depend on George's performance on an oval in Bahrain or a season-ending race in Abu Dhabi."