Given that Mercedes still looked like top dogs in pre-season testing, the burning question at the start of the 2016 F1 season is whether or not the end of 2015 was an aberration.

Once Lewis Hamilton wrapped up the drivers' championship with three races to spare in Austin last autumn, his teammate, Nico Rosberg, went on a tear, proving untouchable in Mexico, Brazil and Abu Dhabi. Ask the two rivals what happened, and you'll probably not be shocked to hear that you get rather divergent responses. Hamilton says he may have let his foot off the throttle with the pressure off.

"I did not do the bare minimum, but I did what I needed to do to finish the year," the 31-year-old Englishman said during pre-season testing. "If you fight for the championship you have to bring that extra five or 10 percent - after I had bagged the title I didn't need that anymore. I used my energy elsewhere."

So there we go; case closed - move along, people, nothing to see here! Or may be not. Nico Rosberg's appraisal of the situation differed in an interview with German magazine "Autobild" this week.

"I don't see it that way. Every one of us wants to win - every race. What came before doesn't matter. I won because I was strong, not because others were weak," Rosberg said, later adding that "everything clicked" after his disappointment in Texas. Asked what this means for 2016, Rosberg replied: "That I can win again."

Bon viveur vs family man

The two teammates don't just sound different when asked touchy questions about one another on the record, their lives have taken rather different turns since they paired up at Mercedes two years ago. Rosberg married his childhood sweetheart Vivian in 2014, their baby Alaïa followed a year later. The man once nicknamed "Britney" (as in Spears) by teammate Mark Webber, aghast at the youngster's clean-cut charm, has adopted rather a low profile away from the F1 circus.

Hamilton, meanwhile, is probably the only driver on the grid gunning for genuine global celebrity status. Take a glance at his Twitter profile and you'd be forgiven for thinking he was either a musician, fashion aficionado or travel show host. Only the picture of his #44 Mercedes gives the game away. To take highlights from the previous week alone, there are shots of Hamilton golfing on top of a New Zealand glacier, partying at a L'Oreal event at Paris Fashion Week, tinkling the ivories (he ditched his old guitar for a piano recently), meeting Sir Paul and Stella McCartney, and crouching with his pooches (British bulldogs, of course) Roscoe and Coco.

Mercedes, sponsored by Hugo Boss and Puma, have even confessed to chiding him for his fashion-focused social media antics - too few of which seem to follow the sponsorship dollars.

Rosberg picked up on precisely this when "Autobild" challenged him, suggesting he might be too straight-laced a family man to really put it all on the line in an F1 title race.

"I see that differently. Red carpets, a party here and a gala there - I don't need all that all the time. I like it too, now and again," Rosberg said. "But for me, the most important thing is that to have success you must know what lifestyle suits you best. And obviously your private life has a huge influence there. I'm happier than I've ever been at home, therefore on track I'm always in balance and have a clear head."

Incredibly, he completed his train of thought without ever actually voicing what seemed to be the unspoken subtext: "unlike Lewis."

If the pre-season banter's anything to go by, both Mercedes men have come ready to rumble. Couple that with Mercedes team boss Toto Wolff saying he expects more fierce infighting this season because of new rules limiting team-to-driver radio communications - making it harder for a team to rein a driver in - and the season could have potential even if Ferrari have failed to close the gap at the top.

Still only the pretender in red

During a record 21-race season - with a street circuit in Baku, Azerbaijan debuting on the calendar, and the return of a German Grand Prix at the Hockenheimring - there's really only one other driver whom observers trust to challenge the Silver Arrows.

Pre-season testing did provide Ferrari and Sebastian Vettel with a glimmer of hope. The Scuderia were the fastest of all at the Catalunya circuit, although Mercedes completed many more miles and seemed like they were unwilling to show their entire hand in terms of one-lap, low-fuel pace. Vettel praised the team for their "significant step forward," but was rather more wary on whether it would be enough to tip the scales.

Qualifying on Saturday in Melbourne should provide a better indicator - especially given that one-lap speed has been Ferrari's major weak spot for years. If Vettel really can put his car on the front row of the grid - to match Ferrari President Sergio Marchionne's stated aim for Melbourne - that would speak volumes for Ferrari's step forward.

For now, though, one must face realities. Since the end of the 2013 season, Mercedes have won every race bar six. Sebastian Vettel is one of only two non-Mercedes drivers - the other being Daniel Ricciardo - to win at all in the past two seasons. The Prancing Horse has quite a fence still to jump.

Mercedes' Toto Wolff even admitted to the "Guardian" this week that it would be better for F1 as a sport if another team joined the fray right at the front - before saying that he'd let his drivers slug it out in any case. They sounded like the words of a confident man.