There are four Americans in the women's quarterfinals in NY for the first time in 15 years after No. 15 Madison Keys grabbed the last four games to top No. 4 seed Elina Svitolina of Ukraine 7-6 (2), 1-6, 6-4 in Monday's last match.
Vandeweghe, 26, was eliminated in the first round at Flushing Meadows past year and has never before gotten this far here.
"I watched the match last night with Venus", said Vandeweghe.
Pliskova never quite found her groove at Flushing Meadows this year as her ferocious serve lacked its usual bite. Vandeweghe was on top from the start of the tie-break and won it 7-4 as Pliskova lost the last two points with unforced errors.
Vandeweghe raced to a 3-0 lead in the first-set tiebreaker, then got an early break in the second set on her way to 3-1 lead, frustrating last year's runner-up with her powerful shots. Soon, she had to serve for the match and the pressure was ramped up.
It was by far the day's most enthralling match, with spectators' roars heard all the way across the grounds at Arthur Ashe Stadium, where Federer was beating No. 33 Philipp Kohlschreiber 6-4, 6-2, 7-5.
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However, the home favourite responded immediately for a third successive break of the set to regain command of the set to move 4-2 ahead before holding serve to move within one game of claiming victory.
When Vandeweghe clinched the match, she dropped to her knees as the crowd roared yet again.
"There's no doubt that there's a special sound when the roof is closed", Vandeweghe said.
Vandeweghe, 25, goes on to face compatriot Madison Keys or Estonia's Kaia Kanepi in the last four. We have to admire Serena and Venus, Lindsay (Davenport), Jennifer (Capriati).
"Maybe I'm going to feel better on the next grand slams".
She said she will take away lessons from the tournament including learning how to win when not playing her best and how to cope with pressure. "Let's make it four for four".
Del Potro long has been popular, but became even more so since returning from three operations on his left wrist that kept him out of Grand Slam action for two years and sent his ranking out of the top 100. But she played confidently on Wednesday against Pliskova, who will lose her No. 1 ranking to Spain's Garbine Muguruza when the new rankings are issued next week.