Novak Djokovic practicing at the ATP Cup. (Twitter/@ATPCup)

In the second edition of the ATP Cup, 12 teams are competing for the title in Melbourne, just one week before the Australian Open. The teams, spread across four groups, are led by some of the best players on the ATP Tour, including Novak Djokovic for Serbia, Rafael Nadal for Spain, Dominic Thiem for Austria, and Daniil Medvedev for Russia.

Last year, Serbia took home the title by defeating Spain in the final. This year, all teams have a star player, making the path to victory for the defending champion more difficult. Day 1 has already seen some upsets Italy taking out Austria, 2-1, after Thiem dropped his opening match to Matteo Berrettini. Thiem returned to the court to team up with Dennis Novak, only to take a second loss to Berrettini (who was paired up with Fabio Fognini). Serbia escaped an upset by winning doubles for a 2-1 win over Canada. 

Before things get too heated, cast your vote: