If Novak Djokovic and Daniil Medvedev win their respective groups, the pair could potentially face off in the final – their fourth in 2021 – with the Serbian leading 2-1.
Novak Djokovic is set to begin his campaign against Norwegian debutant Casper Ruud on Monday with the Serbian world number one aiming to match Roger Federer's record of six ATP Finals titles.
The season-ending men's event is played between the top eight men's singles players and doubles teams and will be held in Turin, Italy with the final scheduled for Nov. 21.
Djokovic, who won his fifth title in 2015 when he defeated Federer in the title clash, was drawn in the 'Green Group' alongside world number three Stefanos Tsitsipas, Russian Andrey Rublev and Ruud.
Defending champion and US Open winner Daniil Medvedev was drawn with Germany's Alexander Zverev, home favourite Matteo Berrettini and Poland's Hubert Hurkacz in the 'Red Group'.
Medvedev, 25, will kick off the singles proceedings in the tournament during the afternoon session on the opening day on Sunday against Hurkacz.
If Djokovic and Medvedev win their respective groups, the pair could potentially face off in the final - their fourth in 2021 - with the Serbian leading 2-1.
Djokovic thrashed Medvedev in straight sets to win his ninth Australian Open title in February while the Russian returned the favour in September to deny the Serbian a historic calendar Grand Slam and win his first major.
Djokovic won their most recent meeting last week in the finals of the Paris Masters where he also clinched the year-end world number one ranking for a record-breaking seventh time.