Stan Wawrinka reaches St. Petersburg Open quarterfinals

Stan Wawrinka kept his injury comeback on track with a hardfought win over Karen Khachanov to reach the quarterfinals of the St. Petersburg Open on Wednesday.

Wawrinka saved two set points in each set on his way to winning 7-6 (10), 7-6 (1) over the fourthseeded Khachanov, who at No. 24 is ranked 64 places above Wawrinka.

Wawrinka's quarterfinal opponent will be either defending champion Damir Dzumhur or Guido Pella.

Second-seeded Fabio Fognini's tournament ended quickly as the Italian lost his opening match 63, 6-4 to Martin Klizan in 1 hour, 15 minutes.

Also Wednesday, fifth-seeded Roberto Bautista Agut beat qualifier Luca Vanni 7-5, 6-2 in their first-round match.

Canadian 19-year-old Denis Shapovalov, seeded seventh, won 7-6 (3), 6-2 against qualifier Adrian Menendez-Maceiras. He'll meet Matteo Berrettini of Italy in the second round for the opportunity to play Klizan in the quarterfinals.

Playing his last tournament before retirement, Russian veteran Mikhail Youzhny prolonged his career by at least one more match with a 7-6 (6), 6-4 win over Mirza Basic.

Youzhny, a former top-10 player with 10 tour titles to his name, goes on to meet Bautista Agut in the second round.

Tiafoe replaces Del Potro at Laver Cup in Chicago

U.S. Open runner-up Juan Martin del Potro has withdrawn from Team World at the Laver Cup this weekend and has been replaced by American Frances Tiafoe.

Del Potro, of Argentina, lost to Novak Djokovic in straight sets in the U.S. Open final.

Djokovic will play for Team Europe at the Laver Cup, which begins Friday at United Center. Each team has six players, including Roger Federer (Team Europe) and Kevin Anderson (Team World). The event features bestof-three set singles and doubles. The final is Sunday.

Tiafoe played for Team World at the inaugural Laver Cup in Prague last year. He lost to Croatia's Borna Coric in a deciding five-set match in the Davis Cup semifinals last weekend.

Tsonga loses to defending champion at Moselle Open

Jo-Wilfried Tsonga made an unsuccessful return to competition on Tuesday, losing 6-7 (5), 6-3, 64 to defending champion Peter Gojowczyk of Germany in the first round of the Moselle Open.

Tsonga, a three-time winner in Metz, played his first match since February after recovering from a knee injury.

Gojowczyk won the tournament as a qualifier last year for his maiden tour title. Against Tsonga, he saved all three break points and hit 17 aces. He will be up against top-seeded Kei Nishikori for a spot in quarterfinals.

Fifth-seeded Nikoloz Basilashvili also advanced by defeating qualifier Kenny De Schepper 6-2, 7-6 (0) while Ugo Humbert rallied from a set down to beat Bernard Tomic 6-7 (5), 6-3, 6-4.

Sharapova cuts season short due to shoulder injury recovery

Maria Sharapova says she will end her 2018 season early, withdrawing from the China Open in Beijing, the Tianjin Open, and the Kremlin Cup in Moscow due to her recovery from a right shoulder injury.

"I will miss competing at each of these tournaments, but it is important that I allow for proper rest and recovery in the upcoming weeks," Sharapova said in a statement on the WTA website.

Sharapova, ranked 24th in the world, was the defending champion at Tianjin.

Five-time major champion Sharapova lost in the first round at Wimbledon and the fourth round at the U.S. Open.

The WTA said Sharapova expects to start her 2019 season at the Shenzhen Open, which begins Dec. 31 in the southeast China city.

Rafael Nadal to skip tournaments in Asia because of bad knee

Rafael Nadal says he will not play in upcoming tournaments in Beijing and Shanghai because of an injured right knee.

Nadal says he and his team decided to skip the Asia swing to recover.

The top-ranked Spaniard retired in the semifinals of the U.S. Open this month because of the knee problem. He had dropped the opening two sets against Juan Martin del Potro when he retired.

The 32-year-old Nadal, who has often dealt with knee pain, won the Beijing tournament last year. He lost the final in Shanghai to Roger Federer.

Nadal, who has won 17 Grand Slam titles, announced his decision not to play in Asia through posts on his Twitter account on Wednesday.

Top-seeded Jelena Ostapenko reaches 2nd round of Korea Open

Top-seeded Jelena Ostapenko beat Lara Arruabarrena 6-3, 6-3 to advance to the second round of the Korea Open on Wednesday.

Ostapenko, the 2017 French Open champion, broke her opponent five times while notching up 32 winners to 29 unforced errors.

"She's a very good player and very consistent," Ostapenko said. "Today was a good match for me, especially for the first round because first rounds are always tough."

Also, second-seeded Kiki Bertens beat Luksika Kumkhum 7-6 (7), 6-2.

Sixth-seeded Hsieh Su-wei defeated Stefanie Voegele 6-2, 6-1, and Evgeniya Rodina outlasted No. 8 Kirsten Flipkens 6-4, 4-6, 75.

At Guangzhou, China, fifthseeded Yulia Putintseva defeated Sabine Lisicke 6-3, 6-3 to reach the quarterfinals of the Guangzhou Open. Also, seventhseeded Vera Lapko overpowered Deniz Khazaniuk 6-2, 7-5.

US Open champion Osaka dominant on return to action in Japan

Naomi Osaka's homecoming couldn't have gone much better.

Playing in her first tournament since winning the U.S. Open, third-seeded Osaka impressed her Japanese fans Wednesday with a powerful 6-2, 6-1 win over Dominika Cibulkova to reach the quarterfinals of the Pan Pacific Open.

Osaka was in control of the second-round match from the outset, breaking Cibulkova's serve in the first game at a sold-out Tachikawa Arena.

"My first match (since the U.S. Open) in Tokyo felt really special," Osaka said. "I didn't really feel pressure, I felt more excitement because I knew that a lot of people were watching this match. I felt really grateful.

"I'm just grateful I could play in front of you guys and want to thank everyone for their support."

The local favorite raced out to a 4-0 lead before Cibulkova finally held to win her first game. Osaka hit three aces to close out the first set. She broke her opponent three more times in the second set to win in just over an hour, hitting 25 winners to just nine unforced errors.

Osaka became the first Japanese player to win a Grand Slam singles title when she upset 23-time Grand Slam champion Serena Williams on Sept. 8 in New York.

Two years ago Osaka lost in the Pan Pacific final to Caroline Wozniacki, who is the top-seeded player this year.

Osaka was born in Japan to a Haitian father and Japanese mother. They were both in attendance Wednesday.