Possibly the main thing you need to know about Roger Federer’s fairly astonishing upset loss to 29-year-old Australian John Millman, who entered Monday night’s U.S. Open fourth-round match with a career losing record of 46-58, was Federer’s terrible struggles with his serve.

    In the first two sets alone, Federer missed 56 of 88 first serves in the 3-6, 7-5, 7-6, (7), 7-6 (3) shocker. For only the fourth time in 74 career Grand Slam tournaments, Federer committed double digit double faults—13 Monday night, including back to back double faults in the final tiebreaker.

     It was Federer’s first loss in 41 Open matches against a player ranked outside the top 50. Millman, currently No. 55, is only one year removed from being ranked 235th after undergoing groin surgery.

    For only the second time in his last 14 Flushiing Meadow appearances, Federer failed to reach the U.S. quarterfinals.

    “I’m probably in a little bit of disbelief,” Millman said. “I have so much respect for Roger and what he’s done for the game. He’s been a hero of mine. He definitely was not at his best tonight. But I’ll take it.”

    Possibly another thing to know about the downside-up events was how Millman was able to soldier on despite a deflating inability to convert seven break points in the second game of the second set. At that point, Federer was up a set and appeared, at the worst, to be subjecting Millman to a tortuous rope-a-dope.

    There were 24 points played in that game. They went to deuce nine times. Yet after the last of those deuces, Federer delivered a 122 mile-per-hour ace and a serve-and-volley winner to hold serve.

    When Federer held his next service game at love, it emphasized his apparent control of the situation, even as Millman was getting no more accomplished than an onset of fatigue. Especially given the suffocating heat and humidity inside breezeless Arthur Ashe Stadium.

     But Federer double faulted on break point in the 10th game to get Millman back on serve and double faulted on game point, setting up another Millman break to lock up the second set.

    By the end of the third, the match had turned into one of those U.S. Open midnight specials, weird and tense and thoroughly unpredictable—and Federer’s last chance at saving the match probably was a botched setup volley on game point that would have given him a 5-2 lead in the fourth.

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