Defending Davis Cup champions Argentina struggle against Italy

Without talisman Juan Martin del Potro, who is starting his season late as a result of his exertions in beating Croatia in November, they could offer little resistance in front of their home fans in Buenos Aires and trail Italy 2-0.

Guido Pella lost 6-3 6-3 6-3 to Paolo Lorenzi before Andreas Seppi defeated Carlos Berlocq 6-1 6-2 1-6 7-6 (8/6).

The main talking point in the build-up to the first-round ties has once again been the absence of the sport's big names.

World number Novak Djokovic was the only member of the top 10 in action, and for a while against Russia's Daniil Medvedev he may have wished he had followed his rivals in sitting out the week.

Medvedev, at 20 an up-and-coming talent, led by a set and 3-0 but Djokovic recovered to win by retirement when leading 3-6 6-4 6-1 1-0 after his opponent was dramatically struck down by cramp.

After his shock loss to Denis Istomin at the Australian Open, Djokovic is no doubt hoping a week with team-mates in front of an adoring crowd in Nis can help him rediscover his best form.

It was a good day all round for Serbia, with Viktor Troicki having saved a match point to beat another young talent Karen Khachanov 6-4 6-7 (3/7) 6-3 1-6 7-6 (6/8) in the opening rubber.

Last year's runners-up Croatia are missing their four leading players but Franko Skugor, the highest-ranked team member at 223, rose to the challenge with a 3-6 6-3 6-4 4-6 7-6 (8/6) victory over 26th-ranked Pablo Carreno Busta of Spain.

The visitors levelled at 1-1 when Roberto Bautista Agut defeated Ante Pavic 6-4 6-2 6-3 and remain heavy favourites to progress.

Debutant Jordan Thompson upstaged Nick Kyrgios as Australia eased into a 2-0 lead over the Czech Republic at Melbourne's historic Kooyong Club.

After his 6-3 6-3 6-4 win over Jiri Vesely, Thompson said on daviscup.com: "(It was) U nbelievably satisfying. That was the best feeling in my life."

Kyrgios fulfilled his part of the bargain by beating Czech debutant Jan Satral 6-2 6-3 6-2.

There were no upsets in Tokyo, where Richard Gasquet and Gilles Simon both won in straight sets against Taro Daniel and Yoshihito Nishioka, respectively, to put France 2-0 up against Japan.

Germany and Belgium, meanwhile, are tied at 1-1.

Davis Cup specialist Steve Darcis shocked Philipp Kohlschreiber in dramatic fashion, winning 6-4 3-6 2-6 7-6 (7/2) 7-6 (5/7), but Alexander Zverev restored equilibrium with a 6-3 6-3 6-4 win against Arthur De Greef.