Sporting theatre is defined by its rivalries. Think Ali and Frazier slugging it out in the boxing ring, McEnroe and Borg going back-and-forth on the tennis court, Coe and Ovett tearing up the track.

As Lewis Hamilton, in his unstoppable Mercedes, canters towards a third world championship, most of us hope he won't get such an easy ride next season. He needs a foe. Formula One is crying out for it.

While nothing can be taken away from his virtuoso displays on the track this season, Hamilton has hardly been made to break a sweat. Indeed after his triumphant victory in Russia on Sunday - his ninth of the season so far - the soon-to-be triple world champion, when pushed by the British media to recall his best racing moment of the year, suddenly had a mild case of amnesia.

"I can't remember," he said.

But the reason Hamilton was struggling to think of one is because there have been few to draw from in a campaign which he has dominated since the sport's curtain raiser in Melbourne seven months ago.

Instead he recalled his duel with Nico Rosberg in the so-called Race of the Century in Bahrain last year. Where Rosberg once took the challenge to his Mercedes team-mate, he has not been able to replicate that kind of form this season.

The dejected German, with his trainers kicked off and slumped in his chair after retiring in Russia, spoke of bad luck playing its part in what, based on last year's performances at least, has been a below-par campaign for him. And he has a case. Two of his last four races have equated to zero points through no fault of his own.

Yet the statistics are still damning.

Hamilton has nine victories. Rosberg has three. Hamilton has out-qualified his team-mate at 12 of the 15 races. And crucially, Hamilton is 73 points ahead of Rosberg in the title race with only four grands prix remaining. If he scores two more points than Rosberg in Austin, there will be no way back for the German.

What a difference a year makes.

Hamilton and Rosberg spent much of last year locked in a brilliant battle, and their rivalry off the track was as fierce as it was on it.

Hamilton's infamous "we are not friends" remark after losing out to his team-mate in Monaco was a fantastic plot line for the sport. Their prang in Belgium a couple of months later was just as good.

But the reality for Rosberg is that he never managed to recover from that incident on the second lap of the Spa-Francorchamps race - one in which, rightly or wrongly, he was apportioned much of the blame by his own team.

And where Hamilton could not even bring himself to describe Rosberg as a pal a little over 12 months ago, earlier this week he was gushing in his praise for his "great team-mate" after Mercedes belatedly sealed the constructors' championship. And why? Put simply, Hamilton no longer sees him as a threat.

Whichever way you look at it, this has been a crushing campaign for Rosberg, and it is difficult to foresee the momentum shifting back in his favour over the winter.

So, who can take the challenge to Hamilton in 2016? Enter stage left, Sebastian Vettel.

"If I hung up my gloves and was just a fan I would want to see the two of us up against each other," said Hamilton after winning in Russia. I am super excited to do that."

And the Briton is not the only one who is enthralled by the prospect - just ask his team boss Toto Wolff.

"They are both in cars that are performing well and it could very well develop into one of the legendary rivalries of the sport," Wolff said. And Wolff is right. Hamilton vs Vettel could be one of Formula One's great rivalries. Scrap that, one of sport's great rivalries.

With 84 victories, 95 pole-positions and six, soon to be seven world championships between them, Hamilton and Vettel are the two outstanding talents of their generation.

Ferrari have raised their game this season and so, too, has Vettel.

The four-times world champion was no more than abject last year, but is a man reborn following his move from Red Bull.

The thought of him locking horns with Hamilton next year is a tantalising one. And it is one that the sport, and arguably both drivers who want to cement their legacies as all-time greats, need.