Tennis-Mboko stuns top seed Gauff to reach Canadian Open quarters

By Rory Carroll

Aug 2 (Reuters) - Canadian teenager Victoria Mboko earned the biggest win of her career on Saturday, beating top seed Coco Gauff 6-1 6-4 to reach the quarterfinals of the Canadian Open in Montreal.

Mboko dropped her racket and covered her face in disbelief as the packed crowd leapt to their feet after the 18-year-old tournament wild card sealed the victory in just over an hour.

"Thank you, you helped me so much," she told the home crowd in French during an on-court interview.

She called her first-ever appearance in the quarterfinals of a WTA 1000 event "incredible," especially after toppling reigning French Open champion Gauff.

Mboko was helped along the way by her error-prone opponent, who never found her rhythm on serve and failed to convert any of her five break point opportunities.

Gauff's sixth double fault set up match point, which Mboko converted when the American's backhand slice drifted into the net.

Despite her disappointment, Gauff hugged Mboko at the net and will look to regroup as she prepares to make a run at a second U.S. Open crown next month.

Mboko will face either Lin Zhu of China or Spaniard Jessica Bouzas Maneiro - both unseeded players - in the quarters.

Earlier, ninth seed Elena Rybakina edged Dayana Yastremska 5-7 6-2 7-5 in their fourth-round battle and will next face another Ukrainian, 24th seed Marta Kostyuk, who came from behind to take out American McCartney Kessler 5-7 6-3 6-3.

On the men's side of the tournament, which is being held in Toronto, 20-year-old Alex Michelsen reached his first quarterfinal of a Masters 1000 event with a 6-3 6-3 win over fellow American Learner Tien.

"It feels really good," Michelsen said.

"It's uncharted territory from this point on, and I'm super happy to be in the quarters for the first time."

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

Khachanov, who has twice reached the semifinals of the tournament, lost to Michelsen in their only prior meeting.

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

Ninth seed De Minaur will next face seventh-seeded American Frances Tiafoe.

Top seed Alexander Zverev was set to take on Argentine Francisco Cerundolo in the night session.