Who can dethrone King Lewis?

Three-time world champion Lewis Hamilton will renew his tense rivalry with Nico Rosberg as Mercedes look to pick up where they left off in Sunday's season-opening Australian Grand Prix.

The German team has ruled Formula One for two years, winning 32 of the 38 races and posing the burning question heading into this year's record, 21-stop season: who is going to stop the Silver Arrows?

Flamboyant Englishman Hamilton, at 31, is bidding for his third win at Melbourne's 5.303 kilometre (3.295 mile) Albert Park street circuit -- one with McLaren Mercedes in 2008, and last year's dominant start-to-finish victory over team-mate Rosberg.

He has savoured a celebrity lifestyle in the downtime after his triumphant 2015 season, and claimed the last six months have been the best of his life.

"Having a blast… travelling, sports, gaming, parties, doing fun stuff… training, sky-diving," he recounted recently.

But now it's down to business after winter testing and Hamilton is ready to reassert his dominance over Rosberg and the rest of the F1 field.

"I have been racing for a long time and always managed to get myself in gear. I am fit and ready to go. I just do me. I do the same thing I always do," he said.

"Coming into this year, I really feel like it's a clean slate. When I arrive at the track, I don't feel like I'm world champion -- that's why I have number 44 on my car and not number one.

"I'm number 44, the same as I was when I first started racing. I was here to beat everyone and that's how I'm going into the first race.

"Testing was just incredible, the best I can remember in my career. The car feels even better than last year's from both a performance and reliability perspective, which is saying something."

Rosberg claimed pole at the last six races of the 2015 season, and swept to victory in the final three grands prix.

But pundits point out that each of those victories came after Hamilton had clinched the drivers’ championship in the United States.

The acrimonious rivalry between the two Mercedes drivers reached breaking point when Rosberg petulantly threw his cap at Hamilton after he sealed the title in Austin.

The German, who again shapes as Hamilton's fiercest championship rival, has vowed to fight all the way during the 2016 title race.

"I look forward to this battle with the world champion," Rosberg said heading into Melbourne.

"He has beaten me for the past two years and he is the benchmark. That is what I am going for and trust me, I will be fighting all the way.

"I need to hope that he doesn't have an awesome season like last year and that for me everything falls into place and I get everything out of it. There is no magic bullet."

Adding spice to this year's exchanges is Mercedes team chief Toto Wolff's vow to stand back and allow Hamilton and Rosberg more freedom to battle on the track, with no team orders from the pit wall.

"The regulations help us because there is much less engineering input, less guidance in terms of how to drive the car," Wolff said.

"It is more up to them how they drive the car. Our role is to step back a little and leave it up to these two to fight it out in the track."

Four-time drivers' champion Sebastian Vettel, who won three GPs last season, looms as the biggest threat to the dominant Mercedes duo in his Ferrari.

Vettel and Ferrari chipped away at the tearaway Mercedes team last year and the German is steadfast in his belief that good times are just around the corner for Ferrari, who have won six times in Melbourne.

"We know Ferrari are very close -- but we're not sure if we're ahead or behind," Rosberg said, after eight days of testing in Barcelona's Circuit de Catalunya.