Quarter-final matches on Wednesday, the 10th day of the US Open (x denotes seeding):
Marin Cilic (CRO x7) v Kei Nishikori (JPN x21)
Nishikori goes into the 15th installment of an intriguing rivalry with an 8-6 record over Cilic. But it's the big Croatian who won their most important meeting -- the 2014 US Open final.
In fact Cilic has won all three of their clashes at the US Open -- beating Nishikori in the second round in 2010 and in the third round in 2012.
Seeded seventh, Cilic has reached two Grand Slam finals in the past 18 months, falling to Roger Federer in the final of the Australian Open in January. He'll be eager to make up for the disappointment of a second-round exit at Wimbledon.
Nishikori, a former world number four, is working his way back after injury cut short his 2017 campaign.
Novak Djokovic (SRB x6) v John Millman (AUS)
Millman, ranked 55th in the world, posted the biggest win of his career when he stunned five-time champion Roger Federer to reach the quarter-finals.
The Swiss great had some advice for Millman on how to extend his giant-killing run against sixth-ranked Wimbledon champion Djokovic.
"He just has to bring it again," Federer said, adding that Millman's intensity was a difference maker in his four-set defeat.
Millman might also benefit if the conditions are as muggy on Wednesday night as they were for his match against Federer, who wilted in the humid weather.
Djokovic, who crushed Millman in their only prior meeting at Queen's Club this year, has been troubled at times by the extreme heat this week.
But since breaking out of his slump in a big way at Wimbledon the Serbian star has gone on to complete his collection of Masters 1000 titles in Cincinnati and stamp himself a favorite to challenge top-seeded defending champion Rafael Nadal for the title.
Naomi Osaka (JPN x20) v Lesia Tsurenko (UKR)
Osaka and Tsurenko are in uncharted territory as they meet for the first time in the first Grand Slam quarter-final for both.
Osaka, 20, came back from a break down in the final set to beat red-hot Aryna Sabalenka of Belarus in the fourth round while 36th-ranked Tsurenko -- who beat world number two Caroline Wozniacki in the second round -- edged Czech teenager Marketa Vondrousova.
They'll likely face the toughest of conditions as they open action on Arthur Ashe Stadium at noon (1600 GMT). That could work in Osaka's favor after Tsurenko struggled in the heat against Vondrousova, battling dizziness before prevailing 6-7 (3/7), 7-5, 6-2.
Carla Suarez Navarro (ESP x30) v Madison Keys (USA x14)
Suarez celebrated her 30th birthday with a victory over five-time Grand Slam winner Maria Sharapova on Monday. The Spaniard had toppled sixth-seeded Caroline Garcia in the previous round but she'll have the crowd against her facing American Keys, last year's runner-up.
Keys, beaten by compatriot Sloane Stephens in the 2017 final, fired 25 winners in a comfortable 6-1, 6-3 fourth-round victory over Dominika Cibulkova.
The 23-year-old has won all three prior meetings with Suarez, the most recent a third-round victory at the Rio Olympics in 2016.