Raising her right fist overhead to celebrate winner after winner, 18-year-old Leylah Fernandez demonstrated that her upset of defending champion Naomi Osaka at the U.S. Open was certainly no fluke by beating another past title winner at Flushing Meadows.

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With grit and guile, and a veteran's poise in the face of a big deficit against a much more accomplished opponent, the unseeded Fernandez grabbed the last five games to defeat 2016 champion Angelique Kerber 4-6, 7-6 (5), 6-2 in the fourth round Sunday in Louis Armstrong Stadium.

Just like against Osaka in Arthur Ashe Stadium two nights earlier, Fernandez dropped the opening set. Just like against Osaka, Fernandez trailed in the second set, too — this time, Kerber led by a break at 4-2.

But for the second match in a row on a big court, the 73rd-ranked Canadian got the crowd on her side, exulting each time she hit one of her on-the-run, impossible-angle groundstrokes. She'd pump a fist. She'd windmill her arms. And she got to do so repeatedly, ending up with a 45-28 edge in winners.

Fernandez is a left-hander who redirects opponent’s shots swiftly and seemingly with ease, sometimes dropping to a knee near the baseline to get the proper leverage. That’s a very similar style to the one Kerber used to reach No. 1 in the rankings and claim three Grand Slam titles.

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Now Fernandez, who only once had been as far as the third round at a major tournament until now, will meet No. 5 seed Elina Svitolina in the quarterfinals.

Fernandez is among several fresh faces making moves at this most tumultuous of U.S. Opens, where the question at the start of each day has become, "Who will pull off a surprise?" — and there tend to be multiple answers by each night.