F1 rivals: 'Dangerous' Hamilton to take on 'impressive' Rosberg in 2016::

It has been a long winter for Mercedes' dueling drivers.

Formula One world champion Lewis Hamilton has been training for the new season in the boxing ring and on the basketball court.

His arch-rival Nico Rosberg, who won the last three races of 2015, was busy babysitting his baby daughter Alaia at home in Monaco.

After a winter of waiting, the duo will renew their rivalry at the Australian Grand Prix on March 20 -- but will Hamilton deliver the knockout blow, or will Rosberg prove he's "The Daddy"?

"If the Lewis Hamilton we know turns up, hungry and fired up, he'll be dangerous," former F1 star Mark Webber told CNN's The Circuit.

"But if Nico can keep up the momentum into 2016, he can start the season really, really well."

Ferrari clocked the headline times over eight days of preseason testing in Barcelona, with Kimi Raikkonen owning the fastest lap overall of one minute, 22.765 seconds, set on 2016's new ultra-soft tire.

Mercedes, however, covered the greatest distance -- the equivalent of more than 19 grands prix -- and was strongly suspected of saving its true pace until Australia.

Rosberg ended last season as "Mr. Perfect," claiming six pole positions and three wins in a row to leave Hamilton trailing.

But the German was only able to assert his dominance after Hamilton had already won the world title at the United States Grand Prix in Austin, a victory sealed when Rosberg made a mistake and ran wide in the closing stages.

"Lewis backed off a sniff, two or three percent, once he'd won the championship," adds Webber, who retired from F1 at the end of 2013. "Nico was thinking, 'I've got to finish with some momentum and ramp it up.'

"I was impressed with how Nico pulled it back at the end of last year. All of a sudden he had this swing in performance and could do no wrong.

"If Nico can keep that up for the first half a dozen races of this year, he will do really well.

"If Lewis turns up wanting to make a huge difference and forgetting the numbers he's already got, he can win. But that's up to Lewis -- he knows he's got to deliver."