Canada's Auger-Aliassime upset in 1st round of Olympics

It was far from the performance Felix Auger-Aliassime was hoping for in his Olympic debut.

Playing on centre court of Tokyo's Ariake Tennis Park on Sunday, Auger-Aliassime was eliminated in just under two hours by a player ranked 190th in the world who was not even scheduled to compete.

Australian Max Purcell, replacing the injured Andy Murray, upset the 15th-ranked Canadian in straight sets 6-4, 7-6 (2) in the first round.

The 20-year-old Auger-Aliassime never got into any kind of rhythm, except for a three-game winning streak that saw him go from down 1-3 to up 4-3 in the second set.

"It's difficult to explain," said the ninth-seeded Auger-Aliassime a few minutes after the loss. "You have to give credit to Max for playing such a good match. Even if he's more of a doubles player, he's dangerous, he serves well.

"Despite everything, I still had chances to do better in this match. I had a very bad service game in the first set, which cost me. After that, I did not find ways to get back into the match. A little in the second set, but it was not enough."

Purcell broke the Canadian to take a 4-3 lead in the first set and won all four points in the next game to go up 5-3.

WATCH | Felix Auger-Aliassime upset in 1st round at Tokyo 2020:

"I played with confidence," said Purcell. "I just had two great tournaments in singles. I won a Challenger just last week.

"I need to make the most every time I get in. I went out there thinking I could win, and I think I had just as much to lose as Felix in my mind."

The Australian earned another break early in the second set to take a 3-1 lead. Auger-Aliassime then strung together his best tennis of the encounter, winning three games in a row to give renewed hope to his team gathered around the court.

But it was short-lived. The two players exchanged serves until the tiebreaker, where Auger-Aliassime fell flat.

"You always have to try to find solutions, to adapt," said the Canadian. "It's difficult, we don't always play our best tennis. That was the case today.

Auger-Aliassime turns his attention to mixed doubles, which kicks off later this week, with teammate Gabriela Dabrowski of Ottawa.

Purcell will next face Germany's Dominik Koepfer, who downed Argentina's Facundo Bagnis 3-6, 6-3, 7-5.

Among the men advancing were third-seeded Stefanos Tsitsipas of Greece, No. 4 Alexander Zverev of Germany, No. 7 Hubert Hurkacz of Poland, No. 8 Diego Schwartzman of Argentina, and No. 12 Karen Khachanov of ROC.

On a good day for the host country, 2016 bronze medallist Kei Nishikori beat fifth-seeded Andrey Rublev 6-3, 6-4.

World No. 1 Barty out

In women's play, top-ranked Ash Barty was upset by 48th-ranked Spanish opponent Sara Sorribes Tormo 6-4, 6-3

Barty's singles defeat came 15 days after she won Wimbledon for her second Grand Slam title.

She struggled with a whopping 55 unforced errors to Sorribes Tormo's 13 and got in only 54 per cent of her first serves compared to her opponent's 83 per cent.

"I never really felt comfortable out there and wasn't able to play the match on my terms," Barty said. "The key to my game is serving well and I wasn't able to do that today. I was a bit erratic and made too many errors."

WATCH | Top-ranked Ash Barty ousted from Tokyo 2020:

Meanwhile, Naomi Osaka is back playing, still winning, and also talking to the media again.

The Japanese superstar who lit the Olympic cauldron defeated 52nd-ranked Zheng Saisai of China 6-1, 6-4 on Sunday in her first match in nearly two months.

Osaka hadn't played since she withdrew from the French Open in May to take a mental health break, revealing that she has dealt with depression. She then sat out Wimbledon.

Osaka stopped to talk with reporters afterward, having said in Paris that she experiences "huge waves of anxiety" before meeting with the media and that she would be skipping news conferences.

"More than anything else I'm just focused on playing tennis," Osaka said. "The Olympics has been a dream of mine since I was a kid so I feel like the break that I took was very needed. I feel definitely a little bit refreshed and I'm happy again."

Also advancing on the women's side was Wimbledon finalist Karolina Pliskova of the Czech Republic, No. 3 Aryna Sabalenka of Belarus, No. 4 Elina Svitolina of Ukraine, No. 7 Garbine Muguruza of Spain and No. 10 Petra Kvitova of the Czech Republic.

Carla Suarez Navarro, the Spaniard who plans to retire this year, beat Ons Jabeur of Tunisia 6-4, 6-1 for her first victory since recovering from Hodgkin's Lymphoma.

Camila Giorgi of Italy eliminated Jennifer Brady, the American who was this year's Australian Open finalist, 6-3, 6-2.