Eight women began the US Open with the chance to finish the tournament on top of the world rankings, but only two remain in contention after the quarter-final line-up was completed on Monday night.
Karolina Pliskova, the current No 1, will retain her position at the top if she emulates her feat of 12 months ago by reaching the final. If she fails to do so, Garbine Muguruza will rise to No 1 for the first time.
Elina Svitolina, the world No 4, had also been in contention to go top of the pile, but the 22-year-old Ukrainian went out of the tournament when she was beaten 7-6, 1-6, 6-4 by Madison Keys, of the United States.
With Coco Vandeweghe also winning on Monday to secure a meeting with Pliskova, the host nation will have four women in the quarter-finals for the first time since 2002. Venus Williams and Sloane Stephens booked their places in the last eight on Sunday.
Keys, the world No 16, has long been regarded as a contender for the biggest prizes, but the 22-year-old has suffered some major disappointments in Grand Slam events and was troubled by injuries earlier this year.
“It means the world to me to make the quarter-finals,” she said after her victory over Svitolina. “It was a really rough start to my year. This is just amazing. I'm really proud of myself for digging deep.”
The first set was close, but Svitolina ran away with the second as the big-hitting Keys started to misfire badly. Svitolina went 4-2 up in the decider, but tightened up with the finishing line in sight.
“I kind of hit a wall at the beginning of the second set,” Keys said. “My energy dropped. Once I got broken in the third, I just kept telling myself: ‘Just try to figure it out. Just get as many balls in as you can.’ I was lucky that I had an amazing crowd and atmosphere. They definitely helped me pull through in that third set.”
In the quarter-finals Keys will face Estonia’s Kaia Kanepi, who beat Russia’s Daria Kasatkina 6-4 6-4. Kanepi has hardy played in the last two years because of a foot problem. Ranked No 418 in the world, she had to qualify to reach the main draw here.
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