For the sixth time, Roger Federer and Rafael Nadal are each a victory away from finally meeting at the US Open, the only Grand Slam tournament where the rivals have never played each other.

Roger Federer of Switzerland celebrates after match point against Philipp Kohlschreiber of Germany on day eight of the US Open tennis tournament at USTA Billie Jean King National Tennis Center. [Photo/Agencies]

Juan Martin del Potro prevented it once and can do it again. Federer plays del Potro in the men's quarterfinals, and top-seeded Nadal faces 19-year-old Russian Andrey Rublev.

Del Potro beat Nadal in the 2009 semifinals at Flushing Meadows, then ended Federer's five-year championship reign by upsetting him in the final. Federer will be the fresher player in their night matchup, having beaten Philipp Kohlschreiber in straight sets Monday, while the 24th-seeded del Potro was overcoming illness and a two-set deficit to rally past No. 6 seed Dominic Thiem in more than 3? hours.

In the women's quarterfinals, No. 1 Karolina Pliskova of the Czech Republic faces No. 20 CoCo Vandeweghe of the US, and 15th-seeded Madison Keys of the U.S. meets 418th-ranked Kaia Kanepi of Estonia, the first qualifier in the US Open women's quarterfinals since Barbara Gerken in 1981.

Agencies