Serena prevails in 3 sets in Open

Faced with her biggest challenge of this U.S. Open fortnight, Serena Williams dug deep when she needed to. The world No. 1 suffered her first loss of a set in the tournament but rallied with her power-ful best en route to a 6-2, 4-6, 6-3 es, win against Simona Halep, advancing to a 10th career semifinal here.

Williams, 34, will take on firsttime Grand Slam tournament semifinalist Karolina Pliskova, the No. 10 seed who upset Venus Williams in the fourth round.

Serena will get a shot at sisterly revenge Thursday night when she and Pliskova face off. No. 2 seed Angelique Kerber meets surprise semifinalist Caroline Wozniacki in the other semifinal.

Serena had been virtually untested in this U.S. Open before Wednesday: She had dropped 20 games in four matches, never losing her serve and facing one break point.

Halep, a 2014 French Open finalist, was the No. 5 seed.

“I knew that I could play a lot better,” Williams said on court after the victory. “I lost my rhythm in the second set. I knew that I had to step it up in the third set.”

Earlier, in a riveting men’s quarterfinal, reigning Wimbledon and Olympic champion Andy Murray lost to No. 6 seed Kei Nishikori 1-6, 6-4, 4-6, 6-1, 7-5.

The loss put Murray, the No. 2 seed, out of a major tournament before the championship match for the first time this year. After runner-up finishes in the Australian and French Opens to Novak Djokovic, Murray won at the All England Club for a second time in his career.

Djokovic, the defending champion here, had moved into the semifinals Tuesday. He will meet Gael Monfils on Friday.