NEW YORK (CBSNewYork/AP) — The tennis world will learn later Tuesday which Williams sister will advance to the US Open semifinals. But it knows now whom Serena or Venus will face.

Roberta Vinci, who was ranked 43rd, outlasted Kristina Mladenovic 6-3, 5-7, 6-4 in the quarterfinals Tuesday. Vinci has reached her first Grand Slam semifinal at age 32.

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The 22-year-old Mladenovic, who had never been past the third round at a major before this tournament, struggled with cramping on a steamy afternoon. Her fourth-round singles match didn’t end until 1 a.m. Monday, then she played doubles later that day.

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Vinci, an Italian, had advanced into the quarterfinal without taking the court Sunday, when 25th-seeded Eugene Bouchard withdrew after sustaining a concussion when she slipped and fell in the locker room two days earlier.

Mladenovic rallied from down a break in the second to force a third set, but had trainers rubbing ice on her legs during changeovers.

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At 3-3 in the final set, the two played a 15-minute game with 10 deuces. Mladenovic had six game points she failed to convert.

After getting broken, the 40th-ranked Frenchwoman asked for a medical timeout. Not eligible under the rules to receive more treatment for cramping, she said it was a different injury. Vinci protested to the chair umpire as Mladenovic had her left thigh wrapped.

It wouldn’t make a difference. Mladenovic repeatedly bent over in discomfort between points, and Vinci won her last two service games to clinch victory after 2 hours, 32 minutes.

Vinci has played on the biggest stages before, winning five major doubles titles with former partner Sara Errani. She had been 0-2 in Grand Slam singles quarterfinals, both at the U.S. Open.

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