Sebastian Vettel looks on after his car broke down during pre-season testing in Bahrain.

Difficulties: Sebastian Vettel looks on after his car broke down during pre-season testing in Bahrain. Photo: AFP

World champion Sebastian Vettel and several of the sport's leading drivers admit the Mercedes duo of Lewis Hamilton and Nico Rosberg go into this weekend's Australian Grand Prix as favourites.

But the German, who has won four consecutive drivers' championships with the Red Bull team,  is a long way from conceding that he and his Australian teammate, Daniel Ricciardo, will have an uphill battle to retain the drivers' and constructors' championships.

When asked on Thursday which team would most likely take the chequered flag on Sunday afternoon, Vettel said: ''For this race Mercedes,  based on winter testing.''

A relaxed Sebastien Vettel.

A relaxed Sebastien Vettel. Photo: AFP

But he was quick to add: ''After three races we will know more.''

Ricciardo also took a pragmatic view - which was to be expected given the travails the champion team has endured in a less than perfect program of pre-season testing with its new car. Red Bull has struggled more than some of its rivals in meeting the radically new technical regulations governing the sport this season.

''The championship is a long way away and I think we are going to develop the car so much through the year. But  I would put my money, in this race, on Mercedes,'' Ricciardo said.

For Vettel, the 2014 season starts in an unusual way.  He will carry the familiar No. 1 on his car as world champion, but will be in the unfamiliar position of not being the favourite when the new campaign starts.

The Mercedes team and the Williams and Force India squads were as impressive in the short testing window as the Red Bulls were disappointing, ensuring that Vettel will face the sort of challenge that he has not had in the past when the Red Bulls were dominant.

''Our pre-season testing and preparation has not been ideal; we are not in the best position for this season,'' Vettel said on Thursday. "But it's a different story when we talk about the championship.

''Two years back Fernando [Alonso, Ferrari's former world champion] was on the grid 1.5 seconds back from the pole but was very close to beating us for the title in the very last race. This race is important, but there are a lot of other races.''

The new regulations were, Vettel admitted, ''a tough step for the teams and drivers to get used to''.

"We know we are not in the best shape, but you can't have everything overnight. You have to go step by step and try to be as strong as you can and give the engineers the best feedback possible.

 ''It's difficult to know what to expect, what the racing will look like, how it will feel. I am going around here to push to the max and do the best I can. We have a strong team, and the target is to finish in the best possible position.''

Alonso's Ferrari outfit was neither good nor poor in the pre-season shootouts, leaving the Spaniard unsure of where he stands in the pecking order.

''It's very difficult to tell how competitive we are. We will know some answers in 24 and 48 hours,'' the dual world champion said.

''The technology this year is a bit complex and it's an unknown situation for everyone. We need to put everything together and maximise what we have.''

Hamilton simply smiled at the plaudits his rivals were giving his team, contenting himself with the observation that formula one was ''very technical this year, everyone is in the same boat''.

But he added that he felt last year's cars were better to drive. ''Now we are in a new phase and it's something that takes time to get used to.''

Felipe Massa, for so long the sidekick to first Michael Schumacher and then Alonso at Ferrari, is relishing his move to English team Williams and is optimistic he and his team can put on a bold show at Albert Park.

''We will get some answers this weekend. I am really happy to be with Williams ... I don't know how competitive we will be with the other teams. I think it's just the beginning, the understanding will be very important in making the car better all the time.

''The team is really motivated, they want to grow and get better, get back to the good times where Williams was in the past. I am really happy with the people I am working with, we all have good ideas with the team.''

For McLaren’s rookie driver Kevin Magnussen, this weekend is a steep learning curve, and the Dane admits he is simply happy to be on the grid.

"I am just really excited to be here and the team has done a really good job preparing me for this,'' he said. "The car looks good, if we can keep developing it as we did over the winter, we will be in a good position.''