Novak Djokovic continued his perfect record at the ATP Cup to help Serbia beat Canada in their opening tie.

The world number one won all eight of his rubbers in the 2020 tournament and made a fine start to this event by battling to a 7-5 7-5 win over Denis Shapovalov in Melbourne.

Milos Raonic had earlier put Canada in front when he beat Dusan Lajovic 6-3 6-4, meaning Djokovic had to return for a decisive doubles clash alongside Filip Krajinovic. 

The Serbians prevailed, winning 7-5 7-6 (7-4) against Shapovalov and Raonic.

"Filip Krajinovic was the key," Djokovic said after the doubles triumph extended his undefeated run to 10. 

"The way he played is phenomenal. He came out with very solid returning. He found his serve, great rhythm. He just played some really key shots in the second set when we needed it the most."

Of his singles win, Djokovic added: "It was a very close match. Playing Shapo is always a great challenge on hard courts. 

"He's such a dynamic, explosive player; very talented. I thought we played on a very high level, so I'm really pleased with how I've started the season.

"This is the best way to kickstart the season, playing for your country.

"We don't get to see crowds in the tennis stadiums these days so much, so it's definitely a blessing. I'm really grateful to see you guys here in the stands."

SPAIN WIN WITHOUT NADAL

Defending champions Spain were without Rafael Nadal for their tie against Australia, but they still prevailed.

Pablo Carreno Busta had few problems seeing off John Millman 6-2 6-4.

And Roberto Bautista Agut ensured the tie was won before the doubles by emerging triumphant in an entertaining encounter with Alex de Minaur, which the Spaniard won 4-6 6-4 6-4.

Nadal, who is battling a back problem, hopes to return on Thursday when Spain take on Greece.

Elsewhere, Austria fell to a 2-1 loss against Italy, as US Open champion Dominic Thiem struggled.

After team-mate Dennis Novak had superbly beaten Fabio Fognini, world number three Thiem fell to a surprise 6-2 6-4 loss against Matteo Berrettini, with Austria going on to lose the decisive doubles.

Andrey Rublev and Daniil Medvedev beat Guido Pella and Diego Schwartzman respectively as Russia produced an impressive performance to beat Argentina.

Elsewhere, at the Murray River Open, Nick Kyrgios made a winning start to his comeback after a year out of action.

He did not have it easy against the unheralded Frenchman Alexandre Muller, but salvaged a 3-6 6-4 7-6 (7-4) victory to book a second-round meeting with fellow Australian Harry Bourchier.