Nitto ATP Finals Day 1 Preview: Former champions Novak Djokovic and Roger Federer to kick off 50th edition of season-ending tournament

The ATP Finals is a season-ending tournament which features the season's top 8 players in a round-robin format followed by a semifinal and final. The 2019 ATP Finals in London would mark the 50th edition of the tournament which started in Tokyo in 1970. It has since been held in 12 different cities before arriving in the British capital in 2009.

For the second time in as many years, the ATP Finals will have eight players from eight different nations. Each of the qualified players in the 2019 field has won at least one title this season and also made a Grand Slam quarterfinal and Masters 1000 semifinal.

Since the present ranking system (2000 points for a Grand Slam winner, 1500 points for an undefeated winner at the ATP Finals, 1000 points for a Masters 1000 winner, 500 points for an ATP 500 tournament winner, and 250 points for an ATP 250 tournament winner) was introduced in 2009, Matteo Berrettini's (2675 points) is the lowest points tally accumulated by the 8th-placed qualifier at the ATP Finals.

During this span, Milos Raonic (4150 points) in 2014 recorded the tournament's highest cut-off for the 8th-placed qualifier.

Five-time winner Novak Djokovic and six-time winner Roger Federer headline the first day of singles action at the 2019 ATP Finals and here is a look at everything you need to know ahead of their respective matches.

#1 Novak Djokovic (x2) vs Matteo Berrettini (x8)

Novak Djokovic vs Matteo Berrettini

Tournament debutant Matteo Berrettini could not have hoped for a bigger test of his credentials when he takes on five-time winner Novak Djokovic in the opening singles match of the 2019 ATP Finals.

This will be the first competitive meeting between the pair.

World No. 2 Djokovic is one of 4 players at the ATP Finals to have triumphed at the tournament at least 5 times, the others being Roger Federer (6), Ivan Lendl (5), and Pete Sampras (5). The Serb's 35 match wins at the season-ending tournament are only dwarfed by Federer (57), Lendl (39), and Boris Becker (36).

Djokovic hasn't lost his opening group match in this tournament since going 0-3 on his debut in 2007. However, 8 of the Serb's 12 losses at the tournament have come in the round-robin stage.

Berrettini is the third Italian player to play at the ATP Finals, following in the footsteps of Corrado Barazzutti and Adriano Panatta. Unlike his illustrious compatriots who failed to win a match at the season-ending tournament, Berrettini would look to become the first player from Italy to record a win at the ATP Finals.

#2 Roger Federer (x3) vs Dominic Thiem (x5)

Dominic Thiem (left) and Roger Federer

In the second singles match on opening day, record six-time champion Federer locks horns with Austrian Dominic Thiem.

In 16 previous appearances at the tournament, Federer has endured an opening group-stage defeat on just 4 occasions, the most recent loss coming against Japan's Kei Nishikori last year.

Thiem is one of 4 players at the 2019 ATP Finals field to have a winning head-to-head record against the Swiss maestro, the others being Novak Djokovic, Rafael Nadal, and defending champion Alexander Zverev.

In 6 previous meetings with Federer, Thiem has triumphed 4 times. In the pair's 2 meetings this year, Thiem emerged victorious on both occasions: in Indian Wells which enabled the Austrian to win his maiden Masters 1000 title, and the Madrid Masters quarterfinals where he saved a match point.

However, Federer did beat Thiem in the 2018 ATP Finals round-robin stage.

Thiem has failed to get past the group stage in his 3 previous appearances at the ATP Finals, winning one match and losing two on each occasion.