Stefanos Tsitsipas and Michalis Pervolarakis are among the tennis stars warming up to compete next week after completing their 14-day mandatory quarantine.
The ATP Cup kicks off on Tuesday 2 February with team Greece making its debut on Wednesday against Australia.
A blockbuster match is set for the next day, with Tsitsipas and Rafael Nadal.
They last played against each other in November, with the Spaniard battling past Tsitsipas 6-4, 4-6, 6-2 at the Nitto ATP semi finals clash.
Earlier, Pervolarakis is set to face Roberto Bautista Agut.
Australia, Spain and Greece compete in the Group B teams with Nadal considered a strong contender, having won four out of six singles matches and earned 250 points last year.
On Wednesday, Pervolarakis will take to the court to face No.38 John Millman, while Tsitsipas meets Australia’s top-ranked men’s player Alex de Minaur.
If no country wins the single matches, it will be up to the doubles match.
A total of 12 countries compete for the title in the five-day tournament, with the event played entirely at Melbourne Park in the week leading up to the Australian Open (starting on 8 February).
The winners of each of the four groups contest the knock-out stages, with the four remaining teams playing the semi-finals.