Everything you need to know about the season-ending ATP Finals

Jannik Sinner and Carlos Alcaraz are poised to add another entry into their rapidly developing rivalry when the ATP Finals open on Sunday without any of the Big Three for the first time in 23 years.

The top-ranked Sinner and No. 3 Alcaraz evenly split the year's Grand Slam titles between them with two apiece and it would be fitting if the pair meet again in Turin.

Sinner and Alcaraz were placed in different groups in Thursday's draw.

The Ilie Nastase Group features Sinner, Daniil Medvedev, Taylor Fritz and Alex de Minaur.

The John Newcombe Group features Alexander Zverev, Alcaraz, Casper Ruud and Andrey Rublev.

After the round-robin stage, the top two finishers in each group advance to the semifinals.

The big name missing is that of defending champion Novak Djokovic, who withdrew on Tuesday due to an unspecified injury.

Djokovic, Federer and Nadal absent

Not since 2001 has the finals been held without at least one of Djokovic, Roger Federer or Rafael Nadal. This season also was the first since 2002 without at least one Grand Slam title for a member of that trio.

Djokovic has won the ATP Finals a record seven times. He beat Sinner in the final last year.

Federer, who retired in 2022, won the event six times after making his debut in 2002; Nadal, who is retiring after playing in the Davis Cup the week after finals, was the runner-up twice at the finals but never won it.

Sinner withdrew from last week's Paris Masters due to a virus and showed up early in Turin for training.

"This is for me the main event of the end of the year," Sinner said.

Decision on Sinner doping still pending

As an Italian, Sinner will be the main focus of attention in Turin.

It's the first time Sinner is playing at home since it was announced before his U.S. Open title that he tested positive in two separate drug tests this year.

A decision to clear Sinner of wrongdoing was appealed by the World Anti-Doping Agency in September and the Switzerland-based Court of Arbitration for Sport is expected to make a final ruling on the case early next year.

Alcaraz is 3-0 vs. Sinner this year

Sinner opened this year by winning the Australian Open to become the first Italian man to win a Grand Slam singles title in nearly a half-century — since Adriano Panatta raised the French Open trophy in 1976.

Alcaraz then claimed the French Open and Wimbledon titles to raise his career total to four Grand Slams.

Sinner responded by winning the U.S. Open.

Alcaraz won all three official meetings with Sinner this year and holds a 6-4 advantage in their career head-to-head rivalry. Last month, Sinner beat Alcaraz in the Six Kings Slam exhibition in Saudi Arabia.

Zverev seeks third title

The only two players in the field to have won the finals are Zverev and Medvedev.

Zverev won in London in 2018 and in Turin in 2021; Medvedev triumphed in 2020, the final year the event was held in London.

Zverev enters in solid form coming off a title at the Paris Masters and leapfrogged Alcaraz into No. 2 in the rankings this week.

Fritz is looking to add another big result after his maiden Grand Slam final at the U.S. Open; Ruud was a finalist in 2022; De Minaur is making his tournament debut; and Rublev is making his fifth straight appearance.

Winner gets $4.8 million

If a player wins all five of his matches en route to the trophy, he will earn $4.8 million — the largest winner's prize on the men's tour.

That's significantly more than what Sinner and Alcaraz earned for their victories at the U.S. Open ($3.6 million) and Wimbledon ($3.45 million) this year.