Belgium's star man David Goffin failed to make an impact against Australia in the first match, losing in straight sets to Alex di Minaur.
The first match of USA vs Great Britain was between Tommy Paul and Dan Evans, which saw the former win by a score of 6-4, 4-6, 6-4.
Australia's Alex di Minaur faced Belgian David Goffin next and picked up a straightforward 6-2, 6-2 victory.
Apart from Djokovic, the Serbian team has players like Miomir Kecmanovic, Filip Krajinovic, Laslo Djere and Dusan Lajovic in their ranks.
Marin Cilic is undoubtedly the star man for the Croatians as he is the one with the most wins for the country in the competition.
The Germans' trump card is Alexander Zverev, one of the best players in the world today and someone who will definitely prove to be a talisman.
The Dutch team comprises of three bright rising stars, Botic van de Zandschulp, Tallon Griekspoor and Tim van Rijthoven.
The Australian team is the second most successful team in the history of the competition with 28 titles.
The South American nation will have the likes of Diego Schwartzman, Francisco Cerundolo and Sebastian Baez representing in the Davis Cup.
The Pole's US Open campaign was cut short after the very first round as she was beaten by 22nd seed Karolina Pliskova 2-6, 6-4, 6-7 (8-10).