Lewis Hamilton is braced for a tougher challenge from Sebastian Vettel for this year's Formula 1 title than he had battling Nico Rosberg.
While team-mates at Mercedes Hamilton and Rosberg spent three years battling exclusively for the drivers' title, with Rosberg finally getting the better of Hamilton in 2016.
After Ferrari driver Vettel won the 2017 season-opening Australian Grand Prix, Hamilton was asked if he faced a tougher test from the four-time champion than the one he got alongside Rosberg.
He replied: "Definitely, definitely. I think this year we're seeing the best drivers at the top.
"Obviously it would be great to have Fernando [Alonso] up there, but it doesn't look like that's going to happen anytime soon.
"At least we have a great driver in Sebastian with his four titles, [who had] an incredible surge into Formula 1, continues to be a force and will continue to be for many years to come.
"I'm really grateful to have that fight with him, against Ferrari. It's great."
Hamilton's relationship with Rosberg became fractious at times, with their on-track battles resulting in crashes on more than one occasion.
The Briton even said during pre-season testing that he was enjoying working with new team-mate Valtteri Bottas more than any other because there were no "mind games".
Asked to compare his relationship with Vettel to that of Rosberg, Hamilton said he would not be drawn into such comments.
"I haven't had many races up against Sebastian but we've always had a respectful relationship," he said.
"I think there's a great amount of respect there between us and I'm sure that will continue to grow."
HUNGER TO BE CHAMPION HAS 'FRICKIN' DOUBLED'
Hamilton said earlier this year his defeat at the hands of Rosberg in last year's title fight had made him more determined to succeed in 2017.
He reiterated his belief that what he does away from the track in his personal life is not affecting his driving, and claimed he was hungrier than ever for a fourth crown.
"This winter I've done exactly what I've done every year," he said when asked if his approach was more mature this year.
"It feels that people judge off things they see and if you go to previous years I arrived at the first race just as fit, I was on pole position for the last four years here.
"I always arrive fit and ready, none of those things I do are a distraction and I've done just as much this year.
"I had a fantastic fight the last few years and obviously last year was the closest I ever had but of course I want to win the world championship more than ever before.
"Whilst last year you would think that the hunger couldn't be any more, it's frickin' doubled. I'm ready."