Nadal, who has played in four Davis Cup winning campaigns, has said he intends to take part in the new-look week-long event on home ground in Madrid from November 18-24.
The victor of each group and the two best second-place teams advance to the quarter-finals.
Instead of taking a year to select a champion from eight teams in the elite world group, the finals will be held over one week, from November 18 to 24, in Madrid.
The International Tennis Federation (ITF) and Davis Cup partners Kosmos Tennis carried out the draw at La Real Casa de Correos in Madrid for the first edition of the historic tournament set to be played over one week in one venue.
"'Be careful, the Davis Cup should not become the Piqué Cup", said Roger Federer last August, in a clear indication of his frustration at the meddling of Gerard Piqué, the Barcelona and Spain footballer, in the tennis world. Serbia, the second qualifying seed, advanced to the finals with a 3-2 win over Uzbekistan in February's qualifying, while Japan, the 12th-seeded qualifier, defeated China by the same score.
That is despite Serbia having qualified as one of the 18 nations for the 2019 Davis Cup finals.
To quickly recap, Piqué, 32, is the founder and president of Kosmos, the investment group that has effectively bought control of the Davis Cup for the next 25 years by...
Barcelona defender Gerard Pique says he will "prove wrong" critics of his role in the reform of the Davis Cup.
Semi-finalists automatically qualify for the 2020 Davis Cup finals.
The format has changed from previous years when all ties were held in one of the competing teams' countries.
"Rafa said he will play and Kei Nishikori will play for Japan and many other players this weekend have given us positive feedback", David Haggerty, president of the International Tennis Federation (ITF) told Reuters.
Pique's participation in the team tennis competition of 119 years of history has generated the annoyance of some important figures in the sport, such as the Australian Lleyton Hewitt, who will captain his country in the event, or the Swiss Roger Federer, who even suggested that the tournament was in danger of becoming the "Pique Cup".
"We understand that we are new in this tennis world, and we want to respect everyone and how the calendar is structured right now". Each session will include two singles matches and a doubles match between two nations.
Group D sees Belgium and Colombia pooled with 28-time champions Australia while Britain, who have been champions on 10 occasions, Kazakhstan and Netherlands make up Group E.