NEW YORK (AP) Roger Federer and Rafael Nadal each need a victory to finally meet at the U.S. Open.
Juan Martin del Potro stopped them before and has a chance to do it again.
Federer faces No. 24 seed del Potro in a matchup of former champions, and the top-seeded Nadal takes on Russian teenager Andrey Rublev on Wednesday in quarterfinal action.
It's the sixth time the longtime rivals have been a victory apiece from meeting at the U.S. Open, the only major where they've never played. One of those was in 2009, when del Potro beat Nadal in the semifinals and then ended Federer's five-year reign in the final.
On the women's side, No. 15 Madison Keys and No. 20 CoCo Vandeweghe can make it an all-American final four, needing victories to join Venus Williams and Sloane Stephens in the semifinals.
Vandeweghe plays top-seeded Karolina Pliskova. Keys faces 418th-ranked qualifier Kaia Kanepi.