- CoCo Vandeweghe and Madison Keys both won Wednesday
- They join Venus Williams and Sloane Stephens in the semifinals
(CNN)The US Open women's singles draw is down to four -- and all of them are American.
On Wednesday afternoon at Arthur Ashe Stadium in Flushing, New York, 20th-seeded CoCo Vandeweghe upset No. 1 Karolina Pliskova, last year's US Open finalist, 7-6(4), 6-3. In the night session, No. 15 Madison Keys cruised against Kaia Kanepi of Estonia, 6-3, 6-3.
"I was real nervous today," Keys said on court as the last American to clinch her spot. "The car ride over, I was definitely feeling it. But I got out here, I felt really good."