Ailing knee knocks defending champ Wawrinka out of U.S. Open

NEW YORK » Stan Wawrinka chose long-term health over a U.S. Open title defense.

The defending champion pulled out of the tournament Friday because of an injured knee, saying he decided to undergo a “medical intervention” and sit out the rest of 2017. He did not provide any specifics about the injury or treatment.

“This was the only solution to make sure I will be able to compete at the top level for many more years,” Wawrinka said in a statement through his agency.

He joins the man he beat in last year’s final at Flushing Meadows, Novak Djokovic, in calling it quits for this season because of injury.

Like Roger Federer last year, Wawrinka couldn’t make it to New York for the season’s final major, which begins Aug. 28.

The fourth-ranked Wawrinka added last year’s title to his 2014 Australian Open and 2015 French Open championships. He got back to the finals in Paris in June, losing to Rafael Nadal, but was eliminated by Daniil Medvedev in the first round at Wimbledon.

The 32-year-old Swiss was clearly bothered by his left knee then, icing it during changeovers. He said after the defeat the knee had been a problem on and off all season and he needed to figure out what was wrong.

Wawrinka finishes with a 26-11 record with just one title this season.

He says he is looking toward and playing in 2018. his

Davis Cup singles matches to remain best of 5 sets

recovery HO CHI MINH CITY, VIETNAM » Davis Cup singles matches will remain best-of-five sets after a proposal for them to be played as bestof-three tiebreak sets was rejected at an annual general meeting of the International Tennis Federation on Friday.

The motion received 63.54 percent support from member nations, but reforms require a two-thirds majority in the voting.

Heat forces Halep to withdraw from Citi Open in quarters

WASHINGTON » Top women’s seed Simona Halep retired from her quarterfinal match at the Citi Open on Friday because of the heat, allowing Russia’s Ekaterina Makarova to advance to the semifinals.

Halep, ranked second on the WTA Tour, retired trailing 1-0 in the third set after she and the seventh-seeded Makarova split the first two.

On the men’s side, eighth-seeded American Jack Sock defeated third-seeded Canadian Milos Raonic 7-5, 6-4 to reach the semifinals.