Djokovic left the court at Arthur Ashe Stadium for a medical timeout - the second time during the tournament he's sought help from a doctor because of harsh weather - during what would become an otherwise straightforward 6-3, 6-4, 6-3 victory over 68th-ranked Joao Sousa of Portugal on Tuesday (NZ time) in the fourth round at Flushing Meadows.
It was most striking during Lesia Tsurenko's 6-7 (3), 7-5, 6-2 win against Marketa Vondrousova, in which both players seemed affected by the temperature and mugginess.
Since her championship, Sharapova has only once made it to the quarterfinals at the U.S. Open - in 2012, when she lost in the semifinals. In the second game of the second set he faced seven break points and landed only four of 22 first serves but still held.
Djokovic, the No. 6 seed in the men's draw, is 28-0 at the US Open when facing an opponent ranked outside the Top 50. Cilic defeated No. 10 seed David Goffin pretty handily in their match on Monday, taking down Goffin in three straight sets.
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 think I really found my serve.
"I've got a lot of respect for Roger".
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.
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And the state's online privacy law has prompted tech companies to promote a weaker federal law that would nullify any state laws. The broadband providers promised they would not block or intentionally slow down other websites in an anticompetitive manner.
For his troubles, John Millman - whose rabid fanbase are called Millminions for what it's worth - now faces another huge task in sixth-seeded Novak Djokovic in his quarter final matchup.
Conversely, it had been five years since Roger Federer exited a US Open before the quarter final stages, last failing in the round of 16 at the 2013 tournament where he was bested by Spaniard Tommy Robrero.
Second seed Federer, who had not dropped a set in his first three matches, was uncharacteristically sloppy, committing 77 unforced errors and 10 double faults while landing just 49 percent of his first serves.
Kei Nishikori is into the quarterfinals of his return to the U.S. Open.
"Felt like a deer in the headlights to begin with, to be honest", he said courtside.
An elbow injury forced the 31-year-old out of the 2017 tournament though Djokovic reached the final 12 months previously, beaten by Stan Wawrinka.