Mercedes may have won the last five constructors' titles in Formula One but Valtteri Bottas expects the Silver Arrows to be chasing rivals Ferrari in Melbourne this weekend.

Since 2014, Mercedes have been the dominant force in F1, adding five successive drivers' titles to their team honours.

Lewis Hamilton has won four of those crowns and heads into the new season as a double-defending champion.

However, Bottas is not convinced the German team have the package to push Ferrari at the Australian Grand Prix after mixed fortunes in pre-season testing.

"What we see from testing, we think [we are underdogs]," Bottas told reporters in Melbourne. "We're going to be kind of chasing.

"It seems like they [Ferrari] had a few good tenths [advantage], but here it is such a different track.

"And we don't know how much they've improved.

"I'm sure with analysing everything and making some improvements we've been able to recover some of that, but how much is only guessing.

"They have a very stable platform, and we definitely have work to do on that. I'm confident the car will be better here [than in testing], but if it's enough, we'll find out."

He added: "We are definitely in the fight and we know we have a strong team. It's a massively long season, and always with some regulation changes like this year is going to be a lot about how much you can improve the car, because the cars in Abu Dhabi are going to be so much quicker than this weekend. 

"So whoever is quickest this weekend, it doesn't really matter as long as it's close. It matters who improves the most."

And it is not only the threat of Ferrari that concerns Bottas, the Finn also expecting Red Bull to go well with their new Honda engines.

"We're still quite unsure about how Red Bull will be," said Bottas. "We think they're going to be strong because Honda looks strong now as well and they've always had a good car.

"Over the past two years, the way they've been able to improve the car during the year has been pretty rapid, so for sure they're going to be a threat as well."