World number one Novak Djokovic and second-ranked Rafael Nadal will headline a slimmed-down field at the coronavirus-hit ATP Cup, organisers said with the tournament cut in half to 12 teams.
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Serbia beat Spain in the final of the inaugural ATP Cup
The innovative championship debuted across three Australian cities -- Perth, Brisbane and Sydney -- in January last year with 24 nations split into six groups ahead of a finals series.
Djokovic's Serbia emerged triumphant, overpowering Nadal's Spain to win the inaugural title.
But the onslaught of Covid-19 forced a radical change to how the 2021 season will look, with the Australian Open pushed back three weeks to February 8.
Players will arrive in Australia from January 15 and undergo a mandatory two-week quarantine before the ATP Cup is held alongside two WTA 500 and two ATP 250 events, all in Melbourne in the week leading into the Grand Slam.
Teams' qualified for the ATP Cup based of men's singles rankings, with Austria, Russia, Greece, Germany, Argentina, Italy, Japan, France and Canada also making the grade.
Australia was included as host nation, but without showman Nick Kyrgios, who was not on the team sheet.
All of the world's top 10 players will take part, except Roger Federer who has pulled out of the Australian Open for the first time in his career as he continues his recovery from two rounds of knee surgery.
ATP Finals champion Daniil Medvedev headlines a strong Russian team alongside fellow top 10 star Andrey Rublev, while world No.3 Dominic Thiem will try to take Austria to glory.
"The players are looking forward to stepping up and representing their countries again, and the field, including defending champions Serbia and finalists Spain, is strong," said tournament director Tom Larner.
"This is a format that shows off the passion of the players and we're expecting some spectacular tennis action."
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The 12 teams will be divided into four groups of three with the winners of each group contesting the knock-outs and the four remaining progressing to the semi-finals.
Each tie will be comprised of two singles matches and one doubles. The draw will be made on January 20 ahead of the tournament starting on February 1.
- Serbia (Novak Djokovic, Dusan Lajovic, Filip Krajinovic, Nikola Cacic)
- Argentina (Diego Schwartzman, Guido Pella, Horacio Zeballos, Maximo Gonzalez)
- Spain (Rafael Nadal, Roberto Bautista Agut, Marcel Granollers, Pablo Carreno Busta)
- Italy (Matteo Berrettini, Fabio Fognini, Simone Bolelli, Andrea Vavassori)
- Austria (Dominic Thiem, Dennis Novak, Philipp Oswald, Tristan-Samuel Weissborn)
- Japan (Kei Nishikori, Yoshihito Nishioka, Ben McLachlan, Toshihide Matsui)
- Russia (Daniil Medvedev, Andrey Rublev, Aslan Karatsev, Evgeny Donskoy)
- France (Gael Monfils, Benoit Paire, Nicolas Mahut, Edouard Roger-Vasselin)
- Greece (Stefanos Tsitsipas, Michail Pervolarakis, Markos Kalovelonis, Petros Tsitsipas)
- Canada (Denis Shapovalov, Milos Raonic, Peter Polansky, Steven Diez)
- Germany (Alexander Zverev, Jan-Lennard Struff, Kevin Krawietz, Andreas Mies)
- Australia (Alex de Minaur, John Millman, John Peers, Luke Saville)