CINCINNATI - Second-ranked defending champion Coco Gauff crashed out in her opening match at the WTA and ATP Cincinnati Open, falling to Yulia Putintseva 6-4, 2-6, 6-4 on Thursday.

The second-round shock to America's Paris Olympic flag-bearer stunned a partisan crowd in the US heartland in the final major tuneup for the US Open, where Gauff is defending champion.

Kazakh spoiler Putintseva, ranked 34th, has made a recent habit of upsets, knocking off world number one Iga Swiatek in the Wimbledon third round barely a month ago.

"I'm really proud of myself," said Putintseva. "Even if the crowd was cheering for Coco, they were fair with me.

"These courts are so fast, you have to just play on instinct. That's what I did."

Gauff became the youngest winner at Cincinnati a year ago at age 19 and carried that success into her first Grand Slam triumph at the US Open.

Putintseva will next face Spain's Paula Badosa, who defeated Anna Kalinsyaka 6-3, 6-2.

Third seed Aryna Sabalenka polished her opening-match record at the event by defeating Italy's Elisabetta Cocciaretto 6-3, 6-4 while men's second seed Alexander Zverev also advanced.

Sabalenka, who missed Wimbledon and the Paris Olympics with a shoulder injury, has now won six of seven opening matches at Cincinnati.

"I'm happy with my level in the tough moments," Sabalenka said. "Elisabetta is a difficult opponent. She fought to the last point."

Cocciaretto was treated for a left hip problem midway through the second set and was seen by the trainer for a thigh tape adjustment at changeovers.

Zverev dodged a few raindrops late in the second set before wrapping up an ATP-leading 50th match win this season.

The German, who won the title here in 2021 after losing his first six career matches at the venue, advanced to the third round 6-3, 6-2 over Karen Khachanov.

The victory in 76 minutes was a repeat of the Tokyo Olympic final won by Zverev.

Khachanov committed 26 unforced errors in defeat against a long-time rival whom he now trails 5-2.

Zverev, who confessed to feeling poorly last week in Montreal despite making the quarter-finals, said his form is now much improved.

"I felt well on court. If you feel good in training it's easier to bring it to the match," he said. "I just hope my form can get better. I'm happy I got the win today."

Zverev had no explanation for his 2023 run of success, saying: "It's just been a good year, but I've also had some tough losses."

Hurkacz to face Cobolli

Spain's Pablo Carreno Busta lined up as the German's next opponent after defeating Australian Max Purcell 6-3, 6-3.

Fifth seed Hubert Hurkacz, who made a surprise comeback from July knee surgery by reaching last week's Montreal quarter-finals, won his opening match, defeating Yoshihito Nishioka 3-6, 7-6 (7/4), 6-1.

The Pole worked for more than two hours, dropping 16 aces against his Japanese opponent and saving 17 of 19 break points.

He will bid for the quarter-finals against Italian Flavio Cobolli, who advanced when compatriot Luca Darderi retired trailing 7-6 (7/4), 3-1 with apparent illness.

In the WTA draw, Elena Rybakina was thwarted in her first match since Wimbledon, going down 3-6, 7-6 (7/3), 6-4 as Canadian Leylah Fernandez saved two match points in an upset of the fourth seed.

Rybakina, who missed the Paris Games with acute bronchitis, suffered with 17 double faults -- including on match points. Even 20 aces could not save her afternoon.

Elina Svitolina, a semi-finalist here nine years ago, saw off Spaniard Jessica Bouzas Maneiro 6-4, 6-1 to next take on Sabalenka.

Sabalenka has won their last two matches, including a Roland Garros quarter-final in 2023 and a three-setter in Rome three months ago.

Newly minted Armenian Elina Avanesyan, who only recently changed tennis nationalities, stunned eighth seed Jelena Ostapenko with a 2-6, 6-2, 6-2 fightback.

AFP