Unseeded & Unfazed: Opelka, Mladenovic come up big on US Open's Day 1

These three unseeded competitors found a way to stand out on a busy first day of the 2019 US Open:

Six months after capturing his first ATP singles title on Long Island, Opelka returned to New York to produce a terrific main-draw debut. The 6’ 11'' American topped the No. 11 seed, 6-3, 6-4, 6-7 (6), 6-3, to notch his third Top 20 win on the Grand Slam stage this season. For Fognini, his major disappointment endures. The Italian dropped to 9-12 at Flushing Meadows and has not advanced to the quarterfinals of a major since his lone last eight appearance at the French Open eight years ago.

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In a meeting between two players short on confidence, Mladenovic emerged victorious to take out the 2016 US Open champion, 7-5, 0-6, 6-4. Mladenovic came into the match 0-4 on hard courts against the German, but prevailed in two hours and 24 minutes to flip the script. Mladenovic will meet countrywoman Fiona Ferro in the second round. Kerber, who won Wimbledon last year, finished her North American hard-court swing 0-3, and has advanced to the second week at just one of her past five majors.

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A year ago, Brooksby made his Grand Slam debut at Flushing Meadows. On Monday, with a year of development under his belt, the 18-year-old secured his first tour-level win by defeating the veteran Czech, 6-1, 2-6, 6-4, 6-4. The Sacramento, CA native was the lone American man to advance through the qualifying rounds and maintained his form by overpowering Berdych with 45 winners to 30 unforced errors. Berdych, who has struggled with back and hip injuries for much of the past year, suffered an opening-round defeat in New York for the first time in nine years.

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Wake up every morning with Tennis Channel Live at the US Open, starting at 8 a.m. ET. For three hours leading up to the start of play, Tennis Channel's team will break down upcoming matches, review tournament storylines and focus on everything Flushing Meadows.

Tennis Channel's encore, all-night match coverage will begin every evening at 11 p.m. ET, with the exception of earlier starts on Saturday and Sunday of championship weekend.