Three matches to watch on Monday, the eighth day of the US Open (x denotes seeding):
Aryna Sabalenka (BLR x26) v Naomi Osaka (JPN x20)
It promises to be a slugfest when these hard-hitting 20-year-olds meet for the first time with a US Open quarter-final berth on the line.
Belarusian Sabalenka stretched her winning streak to eight matches in a row with an upset of two-time Wimbledon champion Petra Kvitova in the third round.
Osaka has roared into the last 16, dropping just seven games in three matches, including a 6-0, 6-0 third-round thrashing of Aliaksandra Sasnovich.
Osaka, ranked 19th in the world, has the edge in experience as she tries to improve on her best Grand Slam showing to date -- a fourth-round run at the Australian Open in January.
But Sabalenka is on a roll, winning her first WTA trophy last week in New Haven to come into her first US Open main draw at a career high of 20th in the world.
Roger Federer (SUI x2) v John Millman (AUS)
Now that he's notched the best Grand Slam performance of an injury hampered career, 55th-ranked Australian Millman wants to be more than a stepping stone for five-time US Open champion Federer.
"He's got an aura about him," Millman acknowledged of 20-time Grand Slam winner Federer.
"But I have never been a fan of playing anyone's reputation. When you go out on court, I think it's about engaging in a battle."
World number two Federer, out to end a US Open drought that stretches back to his fifth straight title in 2008, is no stranger to Millman. Although they've played only once, when Millman took a set off Federer in a 2015 loss at Brisbane, the Aussie has trained with Federer in Switzerland.
It seems unlikely, however, that Millman soaked up enough insights to enable him to stop Federer from reaching a possible quarter-final clash with Novak Djokovic.
Novak Djokovic (SRB x6) v Joao Sousa (POR)
Djokovic, who burst out of his slump with a 13th Grand Slam title at Wimbledon, can do his part to set up a 47th career meeting with Federer with a victory over Sousa -- the world No. 68 who is the first Portuguese man to reach the last 16 of a Grand Slam.
Sousa benefitted from the fifth-set retirement of 12th-seeded Pablo Carreno Busta in the second round and edged 17th-seeded Lucas Pouille in four sets in the third.
Djokovic, US Open champion in 2011 and 2015, has won all four prior meetings with Sousa without dropping a set. The No. 6 seed has gone from strength to strength in the first week of the tournament, which he capped with a comprehensive 6-2, 6-3, 6-3 victory over Richard Gasquet.