Novak Djokovic of Serbia plays a backhand in his match against Denis Shapovalov of Canada during the 2021 ATP Cup at Rod Laver Arena on Tuesday in Melbourne, Australia. Photo: VCG

Australian Open champion Novak Djokovic got his season off to a perfect start with a battling win over hot-shot Denis Shapovalov in the ATP Cup Tuesday, but world No.3 Dominic Thiem crashed to defeat.

The Serbian world No.1, who will be chasing a ninth Australian Open crown when the first Grand Slam of the year begins on Monday, was pushed hard before coming through 7-5, 7-5 against the Canadian on Rod Laver Arena. 

Djokovic showed no signs of being hindered by a nasty blister on his racket hand that troubled him at an Adelaide exhibition last week and returned 30 minutes later alongside Filip Frajinovic to play the decisive doubles rubber.

The pair beat Shapovalov and Milos Raonic 7-5, 7-6 (7/4) as defending champions Serbia took the tie against Canada 2-1 in Group A.

"It was a great opening of the season. Playing Shapo is always a great challenge on hard courts, he is such a dynamic, explosive player," said Djokovic, who was fired up by playing in front of a smattering of noisy Serbian fans.

"I thought we both played on a pretty high level, so I'm really pleased with the way I started the season.

"This is a great competition," added Djokovic, who won all eight matches he contested en route to the trophy last year. "We need more competitions where we represent a team, represent our country." 

Serbia beat Rafael Nadal's Spain in the final of the inaugural and hugely popular tournament last year in Sydney - launched as a rival to the Davis Cup.

It has been slimmed down from 24 teams to 12 this year due to the coronavirus, with all matches at Melbourne Park over five days with $7.5 million at stake, rather than the multi-city format employed in 2020.

World No.2 Rafael Nadal pulled out of Spain's opening ATP Cup tie against Australia on Tuesday, complaining of a stiff lower back.

On a cool day, big-serving Raonic got Canada off to a blistering start, crushing Dusan Lajovic 6-3, 6-4 in just 79 minutes to give his team a 1-0 lead, with the former world No.3, now ranked 15, dropping just eight points on serve while sending down 11 aces. It was left to Djokovic to level the tie before ­clinching the doubles rubber.

The Alexander Zverev-led Germany are also in Group A and will play on Wednesday.

While Djokovic tasted victory, US Open champion Thiem, who lost to the Serb in a gripping Australian Open final last year, got his season off to a disappointing start.

He slumped 6-2, 6-4 to Italian world No.10 Matteo Berrettini who never allowed the Austrian to get going with his big-swinging game.

Berrettini was under pressure after Austria took the lead in their Group C clash when 100th-ranked Dennis Novak earned one of the biggest wins of his career, upsetting world No.17 Fabio Fognini 6-3, 6-2.

It sent the tie to a deciding doubles with Thiem returning alongside Novak only to crash again, losing 6-1, 6-4 to Berrettini and Fognini.