Lewis Hamilton returns to Bahrain four months on from winning an 11th race of a dominant 2020 season knowing Mercedes have plenty of questions to answer from an exciting-looking Red Bull.

It was another season to remember for Hamilton in a campaign disrupted heavily by the coronavirus pandemic, the Briton himself contracting the virus late in the season and missing the second leg of a Sakhir double-header a week later.

By winning a seventh Formula One world title, Hamilton levelled Michael Schumacher's all-time record and also surpassed the legendary German for overall race wins (now 95), and he is now going in search of history.

But the evidence in pre-season suggests Mercedes are set for a titanic tussle with Red Bull, whose exciting line-up of Max Verstappen – the 23-year-old many are tipping to finally go toe-to-toe-with Hamilton – and Sergio Perez will be out to lay down a marker at the Bahrain International Circuit in Sakhir.

Many have suggested that F1's technical 2021 changes have redressed the competitive balance and certainly there was evidence to suggest as such at pre-season testing where Mercedes posted the lowest lap count of any team and Red Bull set the pace on two out of the three days.

We have been here before with Mercedes, though, where some have questioned whether their period of dominance – the Silver Arrows winning the constructors' championship seven years running – is finally over, only for the German manufacturers to turn it on when it matters.

This weekend should give us a clearer indication as to the strength of both teams, but that is by no means the only talking point on the grid...

LAST TIME OUT

Red Bull can certainly take heart from a strong end to the 2020 campaign, which saw Verstappen coast to victory at the Abu Dhabi Grand Prix, a race in which Hamilton finished third after returning from his absence due to COVID-19.

In that race, Red Bull were not necessarily favourites but beat Mercedes in a straight-line fight for Verstappen's second triumph of the season – his first coming in round five at the 70th Anniversary Grand Prix.

Perez can also take plenty of confidence from the fact he triumphed at this circuit for the Sakhir Grand Prix a week after Hamilton's last win of 2020, with a power issue in Abu Dhabi meaning his final outing with Racing Point ended in a whimper.

Valtteri Bottas finished second ahead of Hamilton on that occasion and the Finn knows he has a lot to prove against a strong-looking Red Bull line-up, while McLaren cars finished in fifth and sixth and are fancied for another strong campaign after finished third in the constructors' championship.

WHAT TO LOOK OUT FOR IN SAKHIR

There are plenty of sub-plots in play this weekend after a close-season of change in F1.

Most notable is the return of a legend and the arrival of a rookie aiming to emulate his great father.

Two-time world champion Fernando Alonso is back, racing for the rebranded Alpine Team – formerly Renault where the brilliant Spaniard won his two titles.

Mick Schumacher, son of Michael, has sizeable shoes to fill and will start his career on the biggest stage with Haas alongside fellow F1 rookie Nikita Mazepin.

Sebastian Vettel has a new home after ending his association with Ferrari and will race for Aston Martin, who are back in F1 for the first time since 1960, while the Scuderia signed Carlos Sainz Jr from McLaren to line-up alongside Charles Leclerc for 2021.

McLaren consequently turned to amiable Australian Daniel Ricciardo to partner Lando Norris, with the team starting 2021 12 podiums shy of 500.

TOP FIVE OPTA STATS

- Vettel and Hamilton are the drivers to have won the most races at the Bahrain GP (four), and have taken the most pole positions (three).

- In 2014, Mercedes recorded the first out of their 70 one-twos in hybrid-era qualifying in Bahrain (Nico Rosberg first, Hamilton second). The Germans have achieved 78 one-twos; they are two wins away from reaching Ferrari as the team to have secured one-twos in qualifying most often (80).

- Mick Schumacher will race his maiden grand prix in Bahrain eight years, four months and three days after father Michael's final appearance in Brazil 2012. Both will have started in F1 aged 22 years old, but the younger Schumacher will have done so seven months and 16 days earlier than his dad.

- Sainz will be the third Spanish driver to race for Ferrari. In his maiden race for the Scudería, Alfonso de Portago failed to finish in France (1956), but Alonso won in Bahrain (2010).

- Verstappen has retired three times at the Bahrain Grand Prix (four in Sakhir), more than any other race in his F1 career. The Dutchman has the chance to win back-to-back grands prix in F1 for the first time after 120 races.

After an unpredictable 2020 Formula One campaign ended in wholly predictable fashion, the world's best drivers are back for more in 2021.

The coronavirus pandemic delayed the start to last season and prompted serious surgery to the planned race calendar.

At the end of it all, though, Lewis Hamilton and Mercedes again walked away on top of the pile.

As so often in recent years, the task for the rest of the grid this coming year is simply to stop the reigning champion and his Silver Arrow.

While that is easier said than done, of course, the signs in pre-season are promising.

Will testing preparations derail Mercedes in the opening weeks? We are about to find out, as the Bahrain opener is just days away...

MORE HAMILTON AND MERCEDES DOMINANCE?

Hamilton's title in 2020 was his seventh, tying Michael Schumacher's competition record. A new benchmark is on the horizon if the Briton can repeat his success.

That is not the only landmark in Hamilton's sights, either: with 95 wins and 98 pole positions – both F1 highs – he can surely look forward to a pair of century celebrations this year.

But even if this is to be another sublime season for the 36-year-old, he surely will not find it as straightforward as last year.

Hamilton shut out the noise surrounding his future to claim 11 victories in 2020, yet the new contract he belatedly signed at the end of the campaign keeps him with Mercedes only until the end of 2021.

That spells another 12 months of uncertainty for the sport's premier driver, who also does not yet appear entirely at home in the new W12 car.

The Silver Arrows recorded only 304 test laps in pre-season – the fewest of any team – and may require Hamilton and Valtteri Bottas to learn on the job if they are to extend their record-breaking streak of seven straight constructors' championships.

WHO CAN CHALLENGE THE DEFENDING CHAMP?

Mercedes team-mate Bottas has finished second to Hamilton in the past two seasons, but it would be a tough ask to expect him to outperform the 'GOAT' in the same car – even before considering potential issues with that machine.

No, if Hamilton is to be dethroned, Red Bull look the best bet.

Max Verstappen is undoubtedly the chief threat at the Austrian outfit, having qualified ahead of his team-mates on 36 of 38 occasions since Daniel Ricciardo departed (including a 17-0 record against Alex Albon in 2020).

Indeed, Verstappen – third last year – had the fastest lap time in testing, his effort of a minute and 28.960 seconds in Bahrain putting Red Bull on top in pre-season for the first time.

The Dutchman is pessimistic, though, saying: "[Testing] doesn't say anything about pure performance.

"I know people are excited and think we are just saying this, but Mercedes are still the favourites. How can they not be when they have won seven world championships in a row?"

Ferrari can never be counted out, but they are starting a season with two drivers yet to win a world championship (Charles Leclerc and Carlos Sainz) for the first time since 2007, when Felipe Massa and Kimi Raikkonen lined up for the Scuderia. Of course, that year ended with Raikkonen being crowned champion.

ELSEWHERE...

There is no shortage of intrigue away from the top teams, with two big names returning to F1 – albeit only one of the two drivers having previously raced at this level.

Former champion Fernando Alonso is back, joining the rebranded Alpine team, formerly Renault – where the Spaniard won two titles.

Alonso's most recent race win came in Ferrari colours at the 2013 Spanish Grand Prix, since when he has gone 110 events without victory.

If Alpine can be competitive and Alonso belatedly returns to the top step of the podium later in the season, he could break Raikkonen's record of 114 grands prix between triumphs (2013 to 2018).

The 39-year-old needs only three podiums to reach 100 in F1.

At the other end of the spectrum, Mick Schumacher is the familiar name but new face at Haas, forming an all-rookie line-up alongside Nikita Mazepin, his F2 title rival last year.

Schumacher, who won that championship, will debut at Bahrain eight years, four months and three days after father Michael's final race in Brazil in 2012.

Michael was also 22 when he made his F1 bow, although Mick will be seven months and 16 days younger.

Ricciardo has joined McLaren, who are 12 podiums shy of 500, and Aston Martin are back for the first time since 1960, replacing Racing Point and bringing in Sebastian Vettel.

Meanwhile, there will be increased attention paid to Williams' George Russell, who impressed when given a chance with Mercedes at Sakhir 2020, qualifying second and finishing ninth.

Pierre Gasly has become the latest Formula One driver to confirm a positive test for coronavirus.

The Alpha Tauri driver confirmed he is self-isolating and "feeling ok".

Frenchman Gasly wrote on Twitter: "Hello everyone, I hope you're all safe and well.

"I wanted to let you know that I tested positive for COVID-19. I have told everyone I've been in contact with during these last days.

"I'm currently self-isolating and following the protocol set by the local health authorities. I'm feeling ok and will continue to follow my training plan from home while I remain in isolation. Take care."

Six drivers on the grid have now tested positive for coronavirus, with world champion Lewis Hamilton having been among those towards the end of the 2020 season.

Racing Point drivers Sergio Perez and Lance Stroll also missed races due to COVID-19 last year, while Ferrari's Charles Leclerc and Lando Norris of McLaren contracted the virus during the close season.