"What we see from testing, we think [we are underdogs]", Bottas told reporters in Melbourne.
If Hamilton, victor of four of the last five championships, is feeling the pressure the Briton is doing well to hide it. The British driver is once again the man to beat after he picked up an incredible fifth world championship last season.
However, Rosberg admits that Vettel needs to drive a "perfect season" from the cockpit, and fend off the challenge of his new teammate Charles Leclerc.
Last season Hamilton dominated the show after bagging 11 of the final 19 races. "Fun is to win a lot of races and then ultimately you are fighting for the championship", said the 31-year-old Vettel.
"I've got great memories of this track". Ferrari haven't won the constructors' title since 2008 and their last drivers' crown came in 2007 through Kimi Raikkonen.
"As in any team there has to be a number one and a number two in a 50-50 situation".
Williams has endured an extremely tough pre-season after an equally hard 2018 campaign that saw previous drivers Lance Stroll and Sergey Sirotkin score only seven points between them, but the Grove-based outfit are fielding an all-new line-up in Kubica and 2018 FIA Formula 2 champion George Russell.More news: Brexit hangs in balance over tweaked deal
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Mercedes has claimed both Drivers' and Constructors' titles in each year of the hybrid era, and on each occasion has wrapped up the respective championship with at least a race to spare.
"Our optimism is not unfounded", said Red Bull motorsport consultant Helmut Marko.
"It'll be interesting to see how Red Bull's upgrade worked and I know Ferrari usually bring an upgrade to the first race so it will be interesting to see".
Daniel Ricciardo will also hope for better luck at his home race in the yellow and black of Renault, having missed a maiden podium in Melbourne with Red Bull past year when he was hit with a three-place grid penalty for a minor technical infringement.
Also keep an ear out on Off The Ball this weekend.
At a bumpy street circuit where overtaking has been hard, F1 bosses will hope the introduction of new rules can inject spice.
"In the end we are racing for Ferrari and that means we will try to get Ferrari back to where we've been trying to get it back to the last couple of years".