TORONTO: Top-seeded Alexander Zverev advanced to an ATP Toronto Masters quarter-final against defending champion Alexei Popyrin as his fourth-round opponent Francisco Cerundolo was forced to retire with an abdominal injury on Saturday.

Germany`s Zverev secured a 6-4, 1-0 victory, Argentina`s Cerundolo taking a medical timeout after the fifth game and finally calling a halt after less than an hour on court.

Australia`s Popyrin won his ninth straight match in Canada, beating ninth seed Holger Rune 4-6, 6-2, 6-3.

The 26th-ranked Aussie profitted from nearly 40 unforced errors from his Danish opponent, who has been taking occasional advice from Andre Agassi.

With Popyrin on the horizon, Zverev said he was headed back to the practice court after his abbreviated victory, but he paid tribute to Cerundolo first.

`He`s an incredible player, we have a close personal relationship,` Zverev said of Cerundolo. `I know about abdominal injuries.

`You can`t serve or acceler-ate on the forehand. He had tears in his eyes when he had to quit. He didn`t want to disappoint the crowd.

`But they can last from a few days to a few months. I have respect for him he beat me three times before tonight.

Zverev, the 2017 champion, will be playing his fifth quarterfinal in seven Canadian appearance.

Earlier, Popyrin saved a break point with his sixth ace against Rune as he served for victory in the final game, finishing the job with a lob winner which left Rune flat-footed.

Karen Khachanov reached his second straight prestige quarter-final, ambushing eighth seed Casper Ruud 6-4, 7-5 to continue his ATP hot streak.

Khachanov next faces Alex Michelsen, who claimed his first Masters last-eight place with a 6-3, 6-3 victory over fellow American and good friend Learner Tien.

Khachanov was playing his first tournament since reaching the Wimbledon quarter-finals last month.

The world number 16 reeled off 18 straight points on serveover the first and second sets and produced love games in his final two service games of the match.

Norway`s Ruud, playing his second event after skipping Wimbledon because of injury, was never able to gain control, although he rallied from 4-2 down in the second set to level at 4-4 before Khachanov got back on track.

CANADIAN TEEN STUNS GAUFF In Montreal, Canadian teenager Victoria Mboko took down top-seeded American Coco Gauff 6-1, 6-4 on Saturday, thrilling the home crowd as she reached the quarter-finals of the WTA Canadian Open.

Michelsen took full advantage of 42 unforced errors from Tien to close out their match in 81minutes.

The 18-year-old wild card saved all four break points she faced, and broke reigning French Open champion Gauff three times on the way to a comprehensive victory in just 62 minutes.

`I don`t even know what to say still, I was kind of shocked about it all,` said Mboko, add-ing that the support of the home crowd had buoyed her late in the second set. Mboko started the seasonranked333rdinthe world and has worked her way up to 85 but the win over Gauff -who she took to three sets in Rome in May is the biggest win of her career.

Gauff, who had a combined 37 double faults as she struggled through her first two matehes, was caught flat-footed asthe Canadian teen raced through the first set in 25 minutes.

Gauff buckled down in the second, but she was unable to convertthree break chancesin the seventh game coming up short on a drop shot and smacking a forehand into the net on the first two.

She gained another chance only to hit a service return long, then flew a volley wide to give Mboko a game point, duly con-verted when Gauff fired a forehand long.

Down 15-30 in the ninth game, Mboko leveled at 30-30 with a blistering backhand, then closed out the hold for a 5-4 lead.

Serving to stay in the match, Gauff fell in a quick 0-30 hole and double-faulted to give Mboko a match point, on which the American hit a backhand into the net.

Mboko will next play Spain`s Jessica Bouzas Maneiro, who won a see-saw battle with China`s Zhu Lin 7-5, 1-6, 6-2.

Former Wimbledon champion Elena Rybakina out-lasted Dayana Yastremska 5-7, 6-2, 7-5 to book a quarter-final clash with Marta Kostyuk.

Kazakhstan`s Rybakina, the 2022 Wimbledon champion who won her first title in more than a year at Strasbourg in May, was slowed by nine double faults.

But she ultimately had enough to get past Ukraine`s Yastremska, breaking her twice in the third set and sealing it on her fourth match point.She`ll face another Ukrainian in Kostyuk,whocamefrombehind to beat American McCartney Kessler 5-7, 6-3, 6-3.-Agencies