Formula 1's new-look grid will take on a unique and crucial challenge from Friday as 2021 testing begins in Bahrain, with just three days of track action for teams and drivers to prepare for the season.
Less than three months after an intense 2020 campaign ended, 2021's gets up and running at Bahrain's hot and fast Sakhir circuit - rather than the usual Barcelona - with the shortest-ever pre-season ahead of what is set to be the longest-ever F1 season of 23 races.
Car changes and plenty of driver transfers only emphasise the importance of this year's testing for all 10 teams - and all three days will be live on Sky Sports F1 from 7am on Friday.
Get ready to see the new cars and driver-team combinations, as well as some early clues for Mercedes' rivals to see if they have cut the gap to the world champions ahead of their and Lewis Hamilton's eighth title quest.
The many F1 2021 changes ahead of first - and only - test
The teams
F1 welcomes two new team names to the grid this season in Aston Martin and Alpine, after Racing Point and Renault's respective rebrands.
Aston Martin are back in F1 after 61 years away, while Alpine - Renault's performance sub-brand - are a new name to the sport entirely.
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Both have striking new liveries, big ambitions, and multiple world champions joining their ranks ahead of their debut this weekend.
The drivers
Sebastian Vettel has left Ferrari after six years to join Aston Martin alongside Lance Stroll, with the four-time world champion hoping to rediscover his form with the iconic British carmaker.
Alpine, meanwhile, have a superstar signing of their own after luring Fernando Alonso, the 39-year-old who won his two titles with Renault well over a decade ago, back to F1 after a two-year absence.
Title-chasing Red Bull have signed Sergio Perez to partner Max Verstappen, while Daniel Ricciardo has joined McLaren in place of Carlos Sainz - who is now teamed up with Charles Leclerc at Ferrari.
AlphaTauri have brought a rookie to the grid in Yuki Tsunoda, and Haas have an all-rookie line-up in Mick Schumacher, son of F1 legend Michael, and Nikita Mazepin.
The drivers, who usually get at least three days in the car each ahead of a season, are only set to get a day and a half, at most, this year.
The cars
There may not have been a complete car overhaul for 2021 as planned - with that delayed until 2022 due to the Covid-19 pandemic - but there are subtle changes to the cars that teams believe will be "significant" despite a large carry-over from last year's challengers.
The main changes are on the floor with F1 removing downforce from the cars, leaving the teams' aerodynamic experts scrambling to recover speed and steal a march on their rivals.
Sky F1's Martin Brundle suspected a pecking order 'reset' may be upcoming, and we may get a hint of that a testing - where most cars will be hitting the track for the very first time.
Can Mercedes be stopped in '21 and will midfield close in?
Mercedes are heading into the new season on the back of seven consecutive clean sweeps of F1's championships since the hybrid era began, an unprecedented run of success. Cars which are largely the same as last year, when the world champions built one of their most dominant machines, hardly helps their rivals gain an edge.
But there is optimism from the Red Bull camp about their chances, particularly as they gained on Mercedes towards the end of last season - and we should get an intriguing first look at that battle at 2021 testing as both teams have kept their cars and developments rather secret so far.
A Hamilton vs Verstappen title fight would be box-office for F1.
There is also significant interest in the scrap behind them, closer than ever last season as Ferrari dropped from title challengers to midfield battlers. The Scuderia hope to bounce back from their worst season in four decades this year with a revamped car and new engine, aiming to fend off AlphaTauri, Alpine, Aston Martin and a newly-Mercedes-powered-McLaren in the chasing pack, which should close in on the top two teams.
How to watch on Sky Sports F1
There's never been a pre-season testing schedule quite like this - and you can watch it all live on Sky Sports F1 from next Friday as Formula 1 2021 gets fully up and running with three days of action in Bahrain.
With coverage starting early morning on March 12 and running through the weekend, Sky F1 will be the place to be to watch the eight hours of live track action from each day - plus a nightly Round-up show and Ted's Testing Notebook.
Sky F1's Martin Brundle, David Croft, Ted Kravitz, Rachel Brookes and Karun Chandhok will be out in Bahrain to help tell the story of each day's track running and all the big stories of pre-season.
Testing schedule
Friday, March 12
6.50am-11.05am: Day One Morning Session LIVE!
11.55am-4.10pm: Day One Afternoon Session LIVE!
8pm: Testing Wrap - Day One
8.15pm: Ted's Testing Notebook - Day One
Saturday, March 13
6.50am-11.05am: Day Two Morning Session LIVE!
11.55am-4.10pm: Day Two Afternoon Session LIVE!
8pm: Testing Wrap - Day Two
8.15pm: Ted's Testing Notebook - Day Two
Sunday, March 14
6.50am-11.05am: Day Three Morning Session LIVE!
11.55am-4.10pm: Day Three Afternoon Session LIVE!
8pm: Testing Wrap - Day Three
8.15pm: Ted's Testing Notebook - Day Three