The top seed at Flushing Meadows and last year’s runner-up, Pliskova needed to reach the final of the year’s final grand slam to retain pole position in the rankings.

However, the Czech was overpowered by Vandeweghe, whose 7-6 (7-4) 6-3 victory keeps alive the possibility of an all-American last four in the women’s singles. Sloane Stephens and Venus Williams will meet in one semi-final, while Vandeweghe now awaits the winner of Wednesday’s match between compatriot Madison Keys and Kaia Kanepi.

Although Vandeweghe’s performances at regular WTA Tour events in 2017 have been largely underwhelming, she has frequently impressed on the biggest stages.

A semi-finalist at the Australian Open in January, she also reached the last eight at Wimbledon this year and has now equalled her best performance at a slam.

Muguruza, meanwhile, will become the second Spanish number one since the computerised rankings were introduced in 1975.

The 23-year-old, who exited the US Open to Petra Kvitova in round four, follows in the footsteps of Arantxa Sanchez-Vicario.

Although Pliskova battled hard to keep her hopes alive on Wednesday, it was Vandeweghe who proved stronger in the key moments of a contest that featured some predictably hard hitting on both sides of the net.

Vandeweghe started the match superbly, claiming a deserved break in the third game, but the 20th seed was forced to save a set point in the 10th game before moving ahead in a tie-break.

Both players then had chances to break in set two, but Vandeweghe was more clinical - taking two of the three opportunities to come her way - as she added further intrigue to a draw that already appeared wide open.

STATISTICAL BREAKDOWN

Vandeweghe [20] bt Pliskova [1] 7-6 [7-4] 6-3

WINNERS/UNFORCED ERRORS

Vandeweghe - 24/32 Pliskova - 15/21

ACES/DOUBLE FAULTS

Vandeweghe - 5/5 Pliskova - 2/3

BREAK POINTS WON

Vandeweghe - 3/5 Pliskova - 2/7

FIRST SERVE PERCENTAGE

Vandeweghe - 64 Pliskova - 67

PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE

Vandeweghe - 81/40 Pliskova - 71/47

TOTAL POINTS

Vandeweghe - 76 Pliskova - 64

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