Australian qualifier Alexei Popyrin stunned second seed Felix Auger-Aliassime in the first round of the season-opening Adelaide International on Monday as Novak Djokovic was given a hero's welcome in a rare doubles appearance.

On a day of upsets, world number 11 Holger Rune also crashed out, as did women's third seed Daria Kasatkina and fifth seed Danielle Collins.

Canada's Auger-Aliassime was in top form towards the end of 2022, winning three tournaments in October and November before leading Canada to Davis Cup glory when they beat Australia in the final.

He rose to number six in the world and said before the tournament he wanted to ride the wave of momentum into the 2023 season.

But he came unstuck against Popyrin, who dropped out of the top 100 last year, slumping 6-4, 7-6 (7/5).

The 23-year-old Australian attacked at every opportunity, hitting 32 winners, including 12 aces.

Popyrin broke Auger-Aliassime once in the first set and although he went down an early break in the second, he was able to claw back then clinch the tiebreak on his first match point.

"I had a really, really tough season last year," Popyrin said.

"So to come out in my first main draw match of the year and beat a player of his quality, it just shows that the work I did in the off-season is paying off."

Popyrin now plays American Marcos Giron who beat French veteran Richard Gasquet 7-6 (7/5), 6-7 (6/8), 7-5 on Sunday.

Japan's Yoshihito Nishioka downed fifth seed Rune -- the ATP Newcomer of the Year in 2022 after claiming three titles -- in three sets.

Rune, 19, won the first set comfortably but his serve went off the boil and Nishioka came back to win the next two and take the match 2-6, 6-4, 6-4.

In other singles action, Serbia's Miomir Kecmanovic beat Australian Christopher O'Connell 6-4, 6-4 and Frenchman Quentin Halys eased past wildcard Jordan Thompson 6-3, 6-4.

Earlier, fans gave Djokovic a raucous welcome during his first match in Australia in almost two years.

Playing with Canada's Vasek Pospisil, they lost to doubles specialists Tomislav Brkic and Gonzalo Escobar 4-6, 6-3, 10/5 but enjoyed overwhelming crowd support.

The Serbian superstar, who is also playing singles in Adelaide, was deported from the country before the 2022 Australian Open for not being vaccinated against Covid-19 and was subsequently barred from re-entering for three years.

But the ban was lifted in November and he will be attempting to win his 10th Australian Open title later this month.

There was also a major upset in the women's draw when 18-year-old Czech qualifier Linda Noskova beat Kasatkina 6-3, 6-7 (2/7), 6-3.

In a minor upset, world number 21 Elena Rybakina of Kazakhstan, the reigning Wimbledon champion, defeated 2022 Australian Open runner-up Collins 5-7, 6-2, 6-3.

Fourth-seeded Veronika Kudermetova of Russia crushed American Amanda Anisimova 6-3, 6-0, Romanian Irina-Camelia Begu beat another American, Shelby Rogers, 3-6, 7-6 (7/5), 6-1, while Liudmila Samsonova finished too strongly for China's Zhang Shuai, winning 5-7, 6-3, 6-0.