Daniil Medvedev started the defence of his ATP Finals title with a come-from-behind victory over Hubert Hurkacz in the opening round robin match on Sunday.
Medvedev, the world No 2, claimed his sixth successive victory at the Finals with a 6-7, 6-3, 6-4 win against the Polish world No 9 in Turin. The 25-year-old Russian has now won 23 of his past 26 matches.
The first set was dominated by serve as neither player faced any break points, and Hurkacz, who is making his tournament debut, looked on course to close out a comfortable tie-break when he earned four set points. However, Medvedev fought back from 2-6 to 5-6 only for Hurkacz to finally close out the opener at the fourth attempt.
Medvedev, who won his first Grand Slam title at the US Open in September, responded in style to break at the first opportunity in the second set for a 2-0 lead and with the rest of the set staying on serve, levelled the match on his third set point.
The second seed carried that momentum into the decider and again broke Hurkacz's first service game. With the Russian remaining impenetrable on serve, that was all he needed to eventually close out the win in his opening Red Group match.
German world No 3 Alexander Zverev and seventh-ranked Italian Matteo Berrettini complete the group, while the Green Group features Serbian world No 1 Novak Djokovic, fourth-ranked Stefanos Tsitsipas from Greece, Russian world No 5 Andrey Rublev, and eighth-ranked Casper Ruud of Norway.
Djokovic begins his pursuit of a seventh ATP Finals title against Ruud on Monday evening.