Novak Djokovic, Rafael Nadal & Dominic Thiem confirmed at ATP Cup 2021

As the complicated first quarter of the 2021 tennis season gets underway this week, the lineup for the ATP Cup 2021 has been confirmed. The tournament is set to take place from 1 to 5 February as a tune-up for the Australian Open, which kicks off on 8 February.

The 2021 edition of the ATP Cup - just the second ever - is set to feature some of the biggest names in the men's game. World No. 1 Novak Djokovic, World No. 2 Rafael Nadal and World No. 3 Dominic Thiem are going to lead their respective nations at the multi-team event.

The field is set for the 2021 #ATPCup 🏆

— ATPCup (@ATPCup) January 4, 2021

Defending champions Serbia will be led by Novak Djokovic, with Dusan Lajovic, Filip Krajinovic and Nikola Cacic for company. Last year's runners-up Spain meanwhile will feature 20-time Grand Slam champion Rafael Nadal as well as top singles stars Roberto Bautista Agut and Pablo Carreno Busta.

After failing to impress at the inaugural edition of the ATP Cup, US Open champion Dominic Thiem will hope to perform better for Austria this time around. Thiem will be joined by countrymen Denis Novak and Philipp Oswald in Melbourne Park.

The full list of players can be seen here.

Alexander Zverev (Germany), Daniil Medvedev and Andrey Rublev (Russia), Kei Nishikori (Japan), Gael Monfils (France), Denis Shapovalov (Canada) and Stefanos Tsitsipas (Greece) are also set to feature for their respective countries.

Notable exceptions from the field include Karen Khachanov (Russia), Nick Kyrgios (Australia), Felix Auger-Aliassime (Canada) and Jannik Sinner (Italy). These four players are likely to feature in the ATP 250 events instead, to be held in Melbourne the same week.

Qualification for the ATP Cup is based on the ranking of each country’s highest-placed singles player. Australia, however, qualified by virtue of the host wild card.

To deal with the complications brought in by the pandemic, this year's ATP Cup features 12 teams as opposed to last year's 24.

Novak Djokovic and Rafael Nadal on the cusp of history in 2021

Novak Djokovic (L) and Rafael Nadal at the 2020 French Open

The tennis fraternity - as well as the world in general - has been jolted since Novak Djokovic and Serbia's triumph at the ATP Cup last year. The COVID-19 pandemic has brought about many tournament cancellations, financial difficulties and instances of players backing out of events.

However, Novak Djokovic and Rafael Nadal's hegemony at the summit of men's tennis has remained intact. The Serb finished the year as World No. 1 for a record-equaling sixth time (tying Pete Sampras), and is now on the verge of making more history by breaking Roger Federer's record for most weeks at No. 1. Djokovic is now at 302 weeks, and should cross Federer's total of 310 by the first week of March.

Rafael Nadal, however, could prove to be a thorn in the Serb's side. The Spaniard himself is knocking on the doors of history after the World No. 2 equaled Roger Federer's record of 20 Grand Slam titles with a historic 13th French Open triumph.

Although chances of Rafael Nadal overtaking Novak Djokovic are slim, winning the trophy in Melbourne would make him the out-and-out record-holder for Major titles. It would also make him the first man since Roy Emerson to have won two titles at each Grand Slam event.