It will be the absolute premiere for the Russian and for the Greek in the tournament, since they qualified for the first time in their careers.
The 23-year-old Russian arrives with a 59-18 record in an extraordinary 2019 that included four titles for him and another five finals. The Greek, 21, this year reached 50 wins (with 24 losses), while winning two of the five finals he played.
This is the first time since 2009 that there are four players under 23 in the ATP Finals with Tsitsipas, Medvedev, to which Alexander Zverev and Matteo Berrettini join. The Italian is the other debutante of the tournament.
The Andre Agassi Group, it should be remembered, is completed by Rafael Nadal and Alexander Zverev, who will close the day on Monday.
It should be noted that the fight for number one continues at the end of the year. The distance of 640 points that Nadal has in the classification with respect to Novak Djokovic causes that, in case the Serbian wins the unbeaten tournament, to retain the number one, Nadal has to reach the final, being able to leave a single meeting on the way in the 'round robin'.
In this tournament, each match won in the group stage awards 200 points, while the win is semifinals are 600 points and winning the final gives 500 extra points.
For the first time in the history of the tournament, eight Europeans from eight different countries are represented.