Coco Gauff was sent crashing out of the National Bank Open in Montreal in straight sets by Canadian teenager Victoria Mboko.

The 18-year-old, ranked 85 in the world, needed just 62 minutes to beat the top seed 6-1 6-4 and book a place in the quarter-finals.

"Your support was incredible," Mboko told the crowd in French after a chorus of "Ole, Ole, Ole!" chants echoed around the venue. "I'm really happy to win today... It's incredible. I'm so happy to beat such a great champion."

Mboko started the year by tearing up the ITF circuit with five titles, including one as a qualifier and two doubles. She won an incredible 27 matches with one loss, made her WTA Tour debut in March and took Gauff to three sets in Rome in just her second event.

"I was actually really thinking about it a lot during the match," said Canadian prodigy Mboko. "I had flashbacks to when I played her in Rome a little bit. I just remember when she came out playing even better and stepped it up a bit better.

"I wanted to step my game up a little bit more and make sure I matched whatever she was producing, and I wanted to stay right there with her."

She raced through the first set in 25 minutes, breaking the American three times.

The second set was a tighter affair which went on serve for the first 11 games.

Gauff failed to convert three break points throughout the set, Mboko seizing on her sole opportunity to close out the victory.

World No 2 Gauff said: "She's very athletic. She's a great ball striker, and she seems pretty positive out there on the court, doesn't get really too negative.

"I don't know her too well, but l have spoken to her a little bit since Rome.

"I think she has a great support system around her, and I think that's important when you're young and on tour. Hopefully we have many more battles, and I look forward to playing her again in the future."

Mboko's rise 'nothing short of incredible'

Former Wimbledon finalist Genie Bouchard said Mboko's rise "has been nothing short of incredible".

"Anyone who knew her in Canadian tennis would not be surprised," said the recently-retired tennis star. "She has so much power to her game. I remember practising with her when she was 14,15 years old and she was smacking forehands and bowling me off the court, so we all knew she would be really good.

"I'm so happy to see it happening at such a big event like this as well. She seems to be handling the moment really well, taking it all in her stride and using it as motivation."

After her win over Gauff, Bouchard added: "I'm very impressed with how cool, calm and collected she was on the court. She looked much more mature than her 18 years of age. You see her on the court and she's handling it like she's done it a hundred times."

Former Wimbledon finalist Genie Bouchard said Mboko's rise "has been nothing short of incredible".

"Anyone who knew her in Canadian tennis would not be surprised," said the recently-retired tennis star. "She has so much power to her game. I remember practising with her when she was 14,15 years old and she was smacking forehands and bowling me off the court, so we all knew she would be really good.

"I'm so happy to see it happening at such a big event like this as well. She seems to be handling the moment really well, taking it all in her stride and using it as motivation."

After her win over Gauff, Bouchard added: "I'm very impressed with how cool, calm and collected she was on the court. She looked much more mature than her 18 years of age. You see her on the court and she's handling it like she's done it a hundred times."

Osaka dominates Sevastova to reach last eight

Naomi Osaka delivered the second quickest of her career to reach the quarter-finals in Canada, routing Anastasija Sevastova 6-1, 6-0 in 49 minutes in windy conditions.

In doing so, the former world No. 1 has reached the final eight of a WTA 1000 or Grand Slam event for the first time in 19 months and will now face the winner of a night match between fifth-seed Amanda Anisimova of the United States and 10th-seeded Elina Svitolina of Ukraine.

"I had a solid plan coming in here, and it happened to work out very well," Osaka said after the match.

Sixth-seeded Madison Keys of the United States also advanced, topping 11th-seeded Karolina Muchova of Czech Republic 4-6, 6-3, 7-5 in the windy afternoon session. The Australian Open champion will face the winner of a night match between second-seeded Wimbledon champion Iga Swiatek of Poland and 16th-seeded Clara Tauson of Denmark.

Popyrin, De Minaur and Zverev advance in Toronto

On the men's side of the tournament, which is being held in Toronto, defending champion Alexei Popyrin claimed his second consecutive win over a former Top 5 player when he rallied from a set down to defeat fifth seed Holger Rune 4-6 6-2 6-3.

Alex Michelsen reached his first quarter-final of a Masters 1000 event with a 6-3 6-3 win over fellow American Learner Tien.

Michelsen, seeded 26th, will face hard-hitting 11th seed Karen Khachanov, who upset eighth seed Casper Ruud in their fourth round match 6-4 7-5.

Alex de Minaur, who triumphed at last month's Washington Open, advanced to the quarter-finals over fellow Australian Christopher O'Connell via walkover.

Meanwhile, Argentine Francisco Cerundolo was forced to retire early into the second set of his night match with Alexander Zverev due to an abdominal strain. (Sky sports)