Russia's Ian Nepomniachtchi and China's Ding Liren begin battling it out Sunday to become chess world champion after top-ranked Magnus Carlsen, considered one of the best players of all time, opted not to defend his title.

Neither Nepomniachtchi nor Ding -- the world number two and three respectively -- has held the world title, something that has never happened before in a world title match.

And while Russian players have challenged for -- or defended -- the title many times in the past, Ding is the first Chinese player to play for the game's top honour.

However, whoever wins will still stand in the shadow of Norway's Carlsen, who has held the title since 2013 and remains the top-ranked player.

Their match will be played out through April and possibly into early May at a luxury hotel in the Kazakh capital, Astana.

During his 10-year reign, Carlsen has seen off five challengers, including comfortably defeating Nepomniachtchi in December 2021.

He warned at the time that he might not be willing to defend his title again, confirming his decision in July last year, saying he lacked the motivation.

Nevertheless, Carlsen remains on the chess circuit, maintaining his number one world ranking, and picking up the world titles in blitz and rapid formats in 2022.

For some observers, he is not just the best player currently on the circuit, but the best to ever play the game.

- 'Unstoppable minds' -

Former world chess champion Garry Kasparov, who dominated the game during his 15-year title reign between 1985 and 2000, recently dismissed the title match as "an amputated event".

"I can hardly call it a world championship match," Kasparov said during a recent phone-in at the Saint-Louis Chess Club in the United States.

"For me, the world championship match should include the strongest player on the planet, and this match doesn't," he added, while conceding that the match would still be "a great show".

Match organisers FIDE, the game's world governing body, have focused on playing up the stakes.

As well as being the two top-ranked players after Carlsen, Nepomniachtchi and Ding qualified first and second respectively in last year's qualifiers match between eight of the world's top players.

FIDE has dubbed their battle a clash between two "unstoppable minds".

Nepomniachtchi -- who comfortably won the Candidates Tournament over eight of the world's top grandmasters -- will be hoping to erase the memory of his 2021 defeat by Carlsen.

"His recovery and dominating win in the Candidates was grace under pressure and proof that he is open to constructive criticism of his chess weaknesses, some of which he seems to have fixed," said chess writer Cyrus Lakdawala, the author of several books on the 32-year-old player's aggressive style.

Nepomniachtchi, a Russian national, will play under a neutral flag at the match.

French grandmaster Laurent Fressinet, part of the team that supported Carlsen during his preparation for world title defences, identified one problem for the Russian.

"He has not been put under pressure during the Candidates" Tournament, he said, adding that one of his main problems was he struggled to maintain his composure once he loses a game.

- Best of 14 games -

His Chinese adversary Ding Liren does not appear to have that problem -- he snatched second place in the Candidates Tournament, finishing strongly after a shaky start.

The 30-year-old player is back with a vengeance after barely playing between 2020 and 2022 because of the Covid pandemic.

His mental strength is suggested by the 100-game unbeaten streak he enjoyed in 2017-18 which was finally broken by Carlsen.

"His style is positional, complete," Fressinet said.

"Intrinsically, he's stronger than 'Nepo', but he has less practice, no world championship experience," he added.

The former world number two is already China's strongest-ever player.

The world title will go to the best player over 14 games, with the players alternating between playing black and white.

In the event of a tie after the 14 games, the winner will be decided in a rapid chess play-off.

The two-million-euro ($2.2-million) prize fund will be split 60-40 between the winner and the runner-up.