Two candidates have emerged at the front of the queue for Lewis Hamilton's plum Mercedes cockpit this weekend in Bahrain.

Seven time world champion Hamilton has just started a 10-day isolation period in the island Kingdom after testing positive for Covid with mild symptoms.

Immediately, the candidates to replace him starting lining up, but 2020 'super-sub' Nico Hulkenberg does not appear to be one of them.

"No, I'm not on a plane," the German was quoted as saying.

Mercedes reserve Stoffel Vandoorne, however, is boarding a plane on Wednesday, having just tested with the German marque's Formula E team in Valencia.

"It's Mercedes who decides, but I am quite confident," the Belgian is quoted by L'Equipe. "I have always been told that normally if something happens I will get in the car."

Vandoorne also told Sporza news agency on Tuesday: "There is a chance that I will race, but let's wait. Tomorrow I will fly to Bahrain and I will probably hear about it there."

However, another candidate is George Russell, a Mercedes development driver who has earned a strong reputation as he races for Williams in the last two years.

Williams' official reserve driver is British-Korean driver Jack Aitken, who is in Bahrain with Formula 2 and not in contention for the title.

2016 world champion Nico Rosberg thinks his former team should definitely activate the George Russell contingency.

"Petition for Mercedes to race George Russell this weekend!" he wrote on Twitter. "Would be great."

Officially, Mercedes is saying little for now, with a spokesperson confirming only that Vandoorne was always scheduled to travel to Bahrain after the Formula E test.

"We have said that we will announce a replacement driver in due course and that is still the case," the spokesperson said.