Rafael Nadal’s latest attempt to finally clinch the first ATP Finals title of his career began with a loss to eighth seeded USA Taylor Fritz.
The 36-year-old Spaniard, runner-up in 2010 and 2013, lost 7-6 (7-3) 6-1.
Fritz made his debut at the season-ending event and his relentless return was too much for Nadal.
In the same group, Norway’s third seed Casper Ruud got off to a winning start with a 7-6 (7-4) 6-4 victory over Canada’s seventh seed Felix Auger-Aliassime.
The Turin tournament sees eight of the best men’s players of the season split into two groups of four, with the top two advancing to the semi-finals.
Spanish world number one Carlos Alcaraz withdrew due to injury, leading to first alternate Fritz taking his place.
Serbian Novak Djokovic, who is aiming for a record sixth title, will start against Greece’s Stefanos Tsitsipas on Monday, while Daniil Medvedev faces fellow Russian Andrey Rublev in the other game.
Although there are no British players in singles, three men from the country compete in doubles.
Former world number one Joe Salisbury, second seeded with American Rajeev Ram, won 6-3 6-7 (6-8) 10-8 in a roller coaster match against seventh seeds Marcel Granollers and Horacio Zeballos on opening day.
Lloyd Glasspool and his Finnish partner Harri Heliovaara make their debut in the event and the sixth seeds opened with a 7-5 7-6 (7-3) triumph over Marcelo Arevalo and Jean-Julien Rojer.
Neal Skupski, who was part of the best team in the world this year, plays on Monday.
Skupski and his Dutch partner Wes Koolhof enjoyed incredible success in their first year together, winning seven titles, including Masters 1000 victories in Madrid, Montreal and Paris, and ending 2022 as end-of-year world number ones. year.
The pair open Monday’s game in Turin against Australians Nick Kyrgios and Thanasi Kokkinakis.