Vandeweghe knocks world number one Pliskova out of U.S. Open

Sep 6, 2017; New York, NY, USA; CoCo Vandeweghe of the United States returns a shot to Karolina Pliskova of the Czech Republic on day ten of the U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Anthony Gruppuso-USA TODAY Sports

NEW YORK (Reuters) - CoCo Vandeweghe beat world number one Karolina Pliskova 7-6(4) 6-3 to become the third American woman to reach the semi-finals at the U.S. Open on Wednesday.

The 25-year-old New York native fed off the energy of the partisan crowd at Arthur Ashe Stadium, which erupted when Pliskova returned a serve into the net on match point.

Tennis - US Open - Quarterfinals - New York, U.S. - September 6, 2017 - CoCo Vandeweghe of the United States in action against Karolina Pliskova of Czech Republic. REUTERS/Mike Segar

Defeat for the Czech ensured that she would no longer top the WTA rankings when they are released next week.

Pliskova looked frustrated and struggled to find her rhythm throughout the match, serving just two aces while committing three double faults and 21 unforced errors.

"I can play much better than I was playing today. I didn't feel the best," she said in a post-match news conference.

Sept 6 2017; New York, NY, USA; CoCo Vandeweghe of the United States returns a shot to Karolina Pliskova of Czech Republic at the U.S. Open tennis tournament in Ashe Stadium at the USTA Billie Jean King National Tennis Center. Mandatory Credit: Robert Deutsch-USA TODAY Sports

"But I think you're never going to feel your best with the game that she's playing."

Vandeweghe smacked 24 winners, most of them coming from her powerful forehand, while rocketing five aces and saving five of her seven break points.

After wrapping up victory, Vandeweghe briefly fell to her knees before walking over to her box to shake hands and exchange words with her coach, former Wimbledon champion Pat Cash.

Sep 6, 2017; New York, NY, USA; Karolina Pliskova of the Czech Republic returns a shot to CoCo Vandeweghe of the United States on day ten of the U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Anthony Gruppuso-USA TODAY Sports

"Even though we are out here individually, it's a team sport," she said in an on-court interview.

"They work as hard as I do."

Next up for the 20th-seeded Vandeweghe is a showdown with either fellow American Madison Keys or Kaia Kanepi of Estonia.

Tennis - US Open - Quarterfinals - New York, U.S. - September 6, 2017 - Karolina Pliskova of the Czech Republic reacts during loss to CoCo Vandeweghe of the United States. REUTERS/Mike Segar

(Reporting by Rory Carroll; Editing by Toby Davis)

Sep 6, 2017; New York, NY, USA; Karolina Pliskova of the Czech Republic congratulates CoCo Vandeweghe of the United States on her win on day ten of the U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Anthony Gruppuso-USA TODAY Sports