Ten things you must know about next week's Nitto ATP Finals in London

While some of the best 21-and-under players on the ATP Tour are battling it out this week at the Next Gen ATP Finals in Milan, we’re just days away from the Nitto ATP Finals in London, where the best of the best—the Top 8 players in the ATP rankings—will battle it out at the O2 for season-ending glory.

While Rafael Nadal's participation in the event is uncertain, here are 10 things we know for sure about this year’s Nitto ATP Finals:

1. The draw ceremony took place on Tuesday.

The eight men were split into two groups of four; each player will play everyone else in their group, and the top two finishers from each group will move onto the semifinal round. Group A, named for Andre Agassi, will consist of Nadal, Daniil Medvedev, Stefanos Tsitsipas and Alexander Zverev; Group B, named for Bjorn Borg, will consist of Novak Djokovic, Roger Federer, Dominic Thiem and Matteo Berrettini.

The ATP Finals has been naming its round-robin groups after past champions since 2015 to celebrate the heritage of the event. Borg won the ATP Finals in 1979 and 1980, while Agassi won it in 1990.

2. This will be the 50th edition of the ATP Finals.

The inaugural ATP Finals took place in Tokyo in 1970, and since then the season-ending event has moved around to some of the greatest cities in the world, including the four cities that host the Grand Slams: Paris (in 1971), Melbourne (in 1974), New York (1977 to 1989) and, since 2009, London.

3. The eight-man field was set last Friday, with Berrettini earning the last spot.

World No. 9 Roberto Bautista Agut and No. 10 Gael Monfils will be the two alternates in London this year.

This year's ATP Finals draw. (twitter.com/atptour)

4. Federer is the most decorated player in the history of the ATP Finals.

Not only does Federer have more ATP Finals titles than anyone else in history, winning it six times in 2003, 2004, 2006, 2007, 2010 and 2011, but he also has the most match wins in tournament history, with 57, and he will be making his 17th career appearance at the event this year, which is also a record.

5. Federer is one of three former champions in this year’s field.

Djokovic is hot on the heels of Federer in the record books—he’s won the ATP Finals five times, in 2008, 2012, 2013, 2014 and 2015, which ties him for second place all-time alongside Ivan Lendl and Pete Sampras. The only other former champion in this year’s field is Zverev, who won the title last year, beating Federer and Djokovic back-to-back in the semis and final—both in straight sets.

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6. Nadal and Djokovic will be battling it out for year-end No. 1 in London.

No. 1 Nadal goes in with a 640-point cushion over No. 2 Djokovic, but players can earn up to 1,500 points at the ATP Finals, so the year-end No. 1 remains up for grabs. Players earn 200 points for every round-robin match they win; a semifinal win is worth 400 points; a final-round win is worth 500 points.

7. A red-hot Nadal is seeking his first ATP Finals crown.

The ATP Finals is one of the rare trophies missing from Nadal’s resume. His best results have been two finals, in 2010 and 2013, falling to Federer and Djokovic, respectively. But given his recent form, there’s a good chance this could finally be the year—provided he's healthy, of course. The Spaniard has won 31 of 32 matches over the last six months, his only loss in that stretch coming to Federer in the Wimbledon semifinals. He did, however, have to withdraw from last week's Paris Masters before his semifinal match.

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8. Medvedev, Tsitsipas and Berrettini are all making their ATP Finals debuts.

At the start of the year, Medvedev was ranked No. 16, Tsitsipas No. 15 and Berrettini No. 54. They’re now No. 4, No. 6 and No. 8, respectively, following seasons that saw them all reach the semifinals or better at a major for the first time.

9. For the first time in 10 years, half of the ATP Finals field is 23 or younger.

With 23-year-old Medvedev, 21-year-old Tsitsipas, 22-year-old Zverev and 23-year-old Berrettini, this is the first time there are four players 23 or younger in the field since 2009. That year, it was 23-year-old Nadal, 22-year-old Djokovic, 22-year-old Andy Murray and 21-year-old Juan Martin del Potro who accounted for half of the field.

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10. Don't forget about doubles.

Eight teams have qualified for the doubles event at the ATP Finals: Juan Sebastian Cabal and Robert Farah, Lukasz Kubot and Marcelo Melo, Kevin Krawietz and Andreas Mies, Rajeev Ram and Joe Salisbury, Raven Klaasen and Michael Venus, Jean-Julien Rojer and Horia Tecau, Pierre-Hugues Herbert and Nicolas Mahut and Ivan Dodig and Filip Polasek. The Bryan brothers, who have won this event together four times, would have qualified this year, but they ended their season after the US Open.

Round robin action at the ATP Finals kicks off this Sunday, November 10.