George Russell hopes Williams can make a flying start to the Formula One season in Bahrain - but he believes Mercedes are the only team who will be sure they are race-ready.

British driver Russell caught the eye when he replaced Lewis Hamilton at Mercedes for one race last year, after the world champion tested positive for COVID-19 and missed the Sakhir Grand Prix.

He went close to winning that race until a pit-stop error and a puncture late on cost him a probable victory, and he then returned to his regular drive at Williams.

Mercedes have assured Russell, who is part of their junior driver programme, that he can have a racing future with them if his development continues as expected.

That could come as soon as next year, but for now Russell's focus is on delivering for Williams.

The team has been in transition following the takeover by Dorilton Capital, and German motorsport veteran Jost Capito was appointed chief executive officer during the close season.

Russell believes Williams, who failed to score a point last season, should be better placed in 2021 to at least improve on that disappointing outcome.

"We want, the bare minimum, to be fighting with the Haas and the Alfas, as we did last year, and closing the gap to that midfield," Williams said.

"We made nine out of 17 Q2 appearances and that is definitely a thrill. That's got to be almost an aim every weekend for myself and team."

The season begins in Bahrain on March 28, and by then there should be evidence of which teams have made progress since 2020, with testing taking place, also in Bahrain, on the March 12-14 long weekend.

Russell admits it is a waiting game to see how rivals have advanced, or regressed.

"Fingers crossed that they go backwards and we go forwards," he said, in an Instagram chat on Formula One's official page. 

"Ultimately, we may go to Bahrain and see every other team has progressed more than us.

"We may go there and see we've made great progress. Until we get to Bahrain not a single team, probably bar Mercedes, can tell you how they're going to perform."

Russell, 23, has been tipped for a big future in the sport. He also believes Williams, a great name from the history of Formula One, can begin a journey back to the top of the sport.

"The arrival of Jost is massive for the team, really exciting," he said. "The future for Williams and everybody here at Grove [the team's headquarters] is really great.

"Unfortunately, things don't change in a matter of moments in Formula One, but the building blocks are really getting set in stone.

"Jost has loads of experience, he's a great character, and I think he's going to bring a lot of motivation to the team."

Russell was speaking on the day F1 chiefs confirmed the Portuguese Grand Prix on the new season's calendar, with the race inked in for May 2.

It will be the second round of 23 in the championship, with Portugal having returned to the Formula One rota last year for the first time since 1996.

The Formula One season will start a week later than originally scheduled in Bahrain after the Australian Grand Prix was put back to November due to the coronavirus pandemic.

Melbourne's Albert Park Circuit was due to stage the opening race of 2021 on March 21, but F1 revealed a revised calendar on Tuesday.

The Bahrain Grand Prix will be the first of the year on March 28, with the event in Australia now taking place on November 21 - subject to World Motor Sport Council approval.

Travel restrictions as a result of the COVID-19 crisis will prevent the Chinese Grand Prix - which was due to be the third round of the season - going ahead on April 11 and no new date has been set for that race.

Imola is back on the calendar for the second race of the campaign on April 18, while there is a spare date in the calendar of May 2 for a race to be staged and a venue for that weekend will be announced in due course.

The season is due to end with a record 23rd race of the year in Abu Dhabi on December 12 and F1 expects fans to return to the grandstands this year.

"It has been a busy start to the year at Formula 1 and we are pleased to confirm that the number of races planned for the season remains unchanged," said president and CEO of Formula 1 Stefano Domenicali.

"The global pandemic has not yet allowed life to return to normal, but we showed in 2020 that we can race safely as the first international sport to return and we have the experience and plans in place to deliver on our season.

"It is great news that we have already been able to agree a rescheduled date for the Australian Grand Prix in November and are continuing to work with our Chinese colleagues to find a solution to race there in 2021 if something changes.

"We are very excited to announce that Imola will return for the 2021 season and know our fans will be looking forward to the return of Formula 1 after the winter break and our revised season opener in Bahrain. Obviously, the virus situation remains fluid, but we have the experience from last season with all our partners and promoters to adapt accordingly and safely in 2021."

F1 2021 calendar in full:

March 28 – Bahrain (Sakhir)
April 18 - Italy (Imola*)
May 2 - TBC
May 9 – Spain (Barcelona)
May 23 – Monaco (Monaco)
June 6 – Azerbaijan (Baku)
June 13 – Canada (Montreal)
June 27 – France (Le Castellet)
July 4 – Austria (Spielberg)
July 18 – United Kingdom (Silverstone)
August 1 – Hungary (Budapest)
August 29– Belgium (Spa)
September 5 – Netherlands (Zandvoort)
September 12 – Italy (Monza)
September 26 – Russia (Sochi)
October 3 – Singapore (Singapore)
October 10 – Japan (Suzuka)
October 24 – USA (Austin)
October 31 – Mexico (Mexico City)
November 7 – Brazil (Sao Paulo)
November 21 - Australia (Melbourne*)
December 5 - Saudi Arabia (Jeddah**)
December 12 - Abu Dhabi (Yas Island)

*Revisions to calendar are subject to World Motor Sport Council approval **Subject to circuit homologation.