John Millman reacts after winning a point against Roger Federer during the fourth round of the US Open.
Looking slow and exhausted on a sweltering night in Arthur Ashe Stadium, Federer double-faulted 10 times, failed to convert a trio of set points and lost 3-6, 7-5, 7-6 (7), 7-6 (3) in the fourth round to John Millman in a match that began Monday and concluded at almost 1 a.m. on Tuesday.
There was little sign of what was in store for the five-times champion when he took the first set easily, before world No. 55 Millman turned the tables to win the second then held his nerve through two tiebreaks to secure the victory in three hours and 34 minutes.
"I don't think she was struggling so much", Vondrousova said.
The victor will play Novak Djokovic, who easily accounted Joao Sousa of Portugal 6-3, 6-4, 6-3 earlier in the day.
Djokovic, who is coming off a title at Wimbledon, wasn't at the U.S. Open a year ago, when he missed the last half of the season because of an injured right elbow that eventually was surgically repaired this February.
The two-time champion, who is now 28-0 in NY against players outside the Top 50 of the ATP Rankings, is bidding to lift his third US Open title on his first visit to the tournament since reaching the 2016 final.
He will next face either No. 7 seed Marin Cilic - who beat him in the 2014 U.S. Open final - or No. 10 David Goffin.More news: Williams wins first US Open match in two years
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It was the 37-year-old's earliest loss at a slam since the Australian Open in 2015 and the first time he has ever lost to a player ranked outside the top 50 in NY. He is, after all, a five-time champion at the tournament, part of his men's-record haul of 20 Grand Slam titles. Not simply because Federer lost - he entered the day 28-0 at the US Open, and 127-1 in all Grand Slam matches, against foes below No. 50 in the ATP rankings - but how he lost.
Also into the quarterfinals: 2017 runner-up Madison Keys, who overwhelmed No. 29 Dominika Cibulkova 6-1, 6-3 thanks to a 25-7 edge in winners.
The Spaniard will be at that stage for the second time at the US Open, five years after her other run to that round.
Keys has reached at least the quarterfinals in three of the four Grand Slam tournaments this year.
Millman, ranked 55th in the world, was dominated by Federer in the first set but turned the tables on the Swiss to take the second then held his nerve through two tiebreaks to secure the win in three hours and 34 minutes.
"Felt like a deer in the headlights to begin with, to be honest", he said courtside.
Millman confessed to being in "disbelief" while he acknowledged that the second seed was well below par, but he was delighted with the fight he showed to turn the contest on its head, having been a set and a break down. The big win for Navarro comes on her 30th birthday.