Wimbledon champion Marketa Vondrousova moved a step closer to back-to-back grand slam titles by beating Peyton Stearns to reach the US Open quarter-finals.

The 24-year-old Czech, seeded ninth here two months after becoming the first unseeded woman to win at SW19, fell a set behind to Stearns.

But the American youngster, whose powerful forehand accounted for Britain’s Katie Boulter in round three, won just five more games as Vondrousova triumphed 6-7 (3) 6-3 6-2.

“She was playing great from the beginning and I just tried to stay in the game,” said Vondrousova.

“She is a very dangerous player, she has a great future ahead of her and it was a very tough match.

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“I’m very happy. I didn’t expect this, after Wimbledon there was a lot of pressure but I’m feeling good and we’ll see what happens next.”

US Open TennisMadison Keys is also in the last eight (Manu Fernandez/AP)

What happens next is a meeting with Madison Keys, a former Flushing Meadows runner-up who sprung a mild surprise against fellow American Jessica Pegula, the third seed.

Keys, seeded 17, is emulating the form which swept her to the final in 2017 and sunk the highly-fancied Pegula 6-1 6-3.

The 28-year-old said: “It’s always tough having to play a friend but we’ve been doing it all our lives. On court it’s all business but then we go back to being friends.”