Australia has won the second most Davis Cup championships at 28, behind the United States' 32, but is currently quite a way off the 16 teams currently competing in the World Group.
After the opening day of singles action on Friday, Croatia leads Spain 2-0, Italy and Croatia are level at 1-1, Serbia leads Belgium 2-0, the USA leads Brazil 2-0, France leads Israel 2-0, Argentina leads Germany 2-0, Kazakhstan leads Germany 2-0 and Switzerland is tied 1-1 with the Czech Republic.
Djokovic wasted no time after winning the Australian Open to join his Serbian teammates in Charleroi to take on Belgium, and he cruised past Olivier Rochus 6-3, 6-2, 6-2 in the opening clash on Friday.
His teammate Victor Troicki then had a harder time against David Goffin, but eventually prevailed in five sets 1-6, 3-6, 7-6 (5), 6-4, 6-4 after coming back from two sets down to give Serbia a 2-0 advantage.
Defending Davis Cup champions Czech Republic headed to Geneva to take on Switzerland, and Stanislas Wawrinka gave the Swiss the perfect start as he continued on his Australian Open form, beating Czech Lukas Rosol 6-4, 6-3, 6-4.
World No. 6 Tomas Berdych then levelled things up at 1-1, though, when he overcame Swiss No. 3 Henri Laaksonen in four sets, 6-3, 6-2, 6-7 (5), 6-1.
In Jacksonville, Florida, American giant Isner returned after being forced to pull out of the Australian Open to comfortably beat Brazil's Thiago Alves 6-3, 7-6 (4), 6-3. His teammate Sam Querrey then gave the USA the 2-0 advantage beating Thomaz Bellucci 6-3, 6-4, 6-4.
In Vancouver, Canada, Raonic gave the Canadians the edge over last year's runner's-up Spain when he beat Albert Ramos 6-7 (5), 6-4, 6-4, 6-4.
Fellow Canadian Frank Dancevic then beat Marcel Granollers 6-1, 6-2, 6-2, but Spain was without Rafael Nadal, David Ferrer, Nicolas Almagro, Fernando Verdasco and a host of their top stars.
Italy and Croatia are tied at 1-1 in Turin after two tight singles matches. Italian Andreas Seppi beat Ivan Dodig 6-2, 6-7 (2), 6-4, 6-4, and then Croatian Marin Cilic bounced back to beat Paolo Lorenzi 6-1, 6-7 (6), 4-6, 6-3, 6-2.
French pair Jo-Wilfried Tsonga and Richard Gasquet had terrific Australian Opens, and continued on that form to open up a 2-0 advantage over Israel. Tsonga beat Amir Weintraub 6-3, 6-3, 4-6, 7-5 and Gasquet was too good for Dudi Sela, winning 6-3, 6-2, 6-2.
Argentina is well on top of Germany in Buenos Aires after Juan Monaco beat Florian Mayer 6-7 (4), 6-3, 6-3, 6-4, and Carlos Berlocq beat Phillip Kohlschreiber 3-6, 7-5, 2-6, 6-4, 4-5 when the German retired injured.
Kazakhstan also took a 2-0 lead over Austria in Astana with Evgeny Korolev beating Jurgen Melzer 7-6 (4), 6-3, 6-2 and Andrey Golubev downing Andreas Haider-Maurer 7-6 (2), 6-3, 7-6 (5).