By Alan Baldwin
LONDON (Reuters) - Lewis Hamilton is braced for his biggest challenge as he chases a sixth Formula One title and Sebastian Vettel and Ferrari sense this could be the year they finally turn the tables on Mercedes.
The 21-race championship revving up for a fresh start in Melbourne next week is already showing the hallmarks of a classic.
Hamilton, a global superstar as much at home hanging out with celebrities at fashion shows as lapping a race track, has won 51 of the last 100 grands prix for Mercedes and four of the last five championships.
While he can expect to add to his tally of 73 race wins, 18 behind Michael Schumacher's all-time record of 91, the balance of power may be shifting away from Brackley and towards Maranello.
"This is going to be the toughest battle yet...their pace is very good at the moment," the Briton said after suggesting in pre-season testing that Ferrari could be as much as half a second ahead.
Mercedes, seeking to become the first Formula One team to take six successive title doubles, will throw everything at Ferrari, who can afford none of the mistakes of last year.
There are plenty of alluring storylines, from familiar faces in different overalls to youngsters stepping out into the spotlight and those, such as Poland's Robert Kubica with Williams, returning after fearing their F1 careers were over.
A new Honda-Red Bull alliance could reward a more mature Max Verstappen, now in his fifth season but still only 21, while former partners Renault have taken smiling Australian Daniel Ricciardo with them.
Racing Point are starting over, their Force India days consigned to history, with Canadian Lance Stroll joining the team his father Lawrence now owns.
Ferrari fans can see good omens, aware that Schumacher had to wait five years to win a title with the Italian team and that fellow-German Vettel, a four times champion with Red Bull, has reached a similar stage.
Vettel also left pre-season testing in Barcelona with the fastest lap time.
Ross Brawn, Formula One's managing director for motorsport who masterminded Schumacher's championships and also led Mercedes as well as winning titles with his own eponymous team, is among those feeling excited.
"I think we’ve got a vintage season coming up," he told reporters.
"We’ve got all these elements --- Charles Leclerc, Sebastian Vettel, Ferrari under different management, Mercedes will be very strong, we’ve got the new regulations which I think will close the field up a bit...
"I think the performance and reliability of Honda seems a big step up. And then we have a fascinating midfield. All pretty tight and impossible to call, but still seemingly a bit of a gap between the front and midfield."
Monaco's Leclerc, 21, is Ferrari's youngest race driver since 1961 and replaces Kimi Raikkonen, the 2007 world champion who has moved to the Alfa Romeo team previously known as Sauber.
Ferrari have a new boss in Mattia Binotto, replacing Maurizio Arrivabene in a move that has lifted what many saw as a climate of fear hanging over the team.
"Clearly there was some friction in the team between Maurizio and Mattia, it wasn’t smooth. It wasn’t an easy environment last year," said Brawn.
"If you’re going to beat Lewis Hamilton in a Mercedes, you need to be on top of everything.
"I have a feeling this year will be stronger for them...there’s a calmness about the team, and the car looks good, so I think they’ve got every chance this year."
The new regulations have changed the front and rear wings, aimed at making it easier for cars to get closer and overtake, but lap times are unlikely to be much changed.
Formula Two champion George Russell makes his debut at struggling Williams, while Lando Norris steps up at McLaren and Alexander Albon at Toro Rosso -- all British-born but the latter racing for Thailand.
The season ends in Abu Dhabi on Dec.1, the latest finale to a season since 1963.
(Reporting by Alan Baldwin, editing by Toby Davis)