New York - CoCo Vandeweghe reached the US Open semi-finals Wednesday, knocking Karolina Pliskova off her world number one perch.
American 20th seed Vandeweghe claimed a 7-6 (7/4), 6-3 win over the Czech Republic's Pliskova, whose brief eight-week stay as world number one ends with Wimbledon champion Garbine Muguruza taking over.
Vandeweghe's victory means that the US Open will have an all-American semi-final line-up for the first time since 1981 if Madison Keys defeats Estonia's Kaia Kanepi later Wednesday.
"I won the juniors here when I was 16 and dreamed of playing on the real stage," said 25-year-old Vandeweghe, who also made the semi-finals at the Australian Open, beating then world number one Angelique Kerber in the process.
Venus Williams and Sloane Stephens had already set-up an all-American semi-final.
The last time four US women were in the semis was 36 years ago when eventual champion Tracy Austin, Chris Evert, Martina Navratilova and Barbara Potter all made it.
"Let's make it four from four," said Vandeweghe.
Pliskova, who had to save a match point to beat China's Zhang Shuai in the second round, needed to fight back from breaks down in both sets to keep her challenge alive.
But a final break from the American for a 4-2 lead in the second set proved decisive and the match was hers when Pliskova buried a return into the net.