Stan Wawrinka reached the US Open quarter-finals for a fourth successive year on Monday with a 6-4, 6-1, 6-7 (5/7), 6-3 win over Ukraine journeyman Illya Marchenko.
Third seed Wawrinka, a semi-finalist in 2013 and 2015, will take on 2009 champion Juan Martin del Potro for a place in the last-four.
Del Potro, at 142 in the world, is the lowest ranked man in 25 years to reach the last eight.
The Argentine progressed when Austrian eighth seed Dominic Thiem retired from their last-16 tie with a knee injury. Del Potro was leading 6-3, 3-2 when Thiem quit.
Wawrinka had to save a match point in his epic third round win over Dan Evans and has yet to face an opponent ranked inside the top 45.
Pliskova ousts Venus
Karolina Pliskova ruined any chance of another Flushing Meadows sister showdown as she claimed a dramatic 4-6 6-4 7-6(3) win over sixth-seeded Venus Williams to reach the U.S. Open quarter-finals.
At 36-years-old and the oldest remaining player in the draw, Williams battled until the bitter end as her 24-year-old Czech opponent needed five match points to finally put away the two-time champion.
Since the draw was unveiled tennis fans had circled a potential semi-final between the sport's most famous siblings on American tennis's biggest stage where world number one Serena and Venus have met five times, including twice in the finals.
Now it is 10th-seeded Pliskova, who will play Poland's Agnieszka Radwanska or Croatia's Ana Konjuh in the quarters, that would need to complete a Williams double to reach her first grand slam final.
Serena, looking to continue her drive for a record seventh U.S. Open title, will meet Kazakhstan's Yaroslava Shvedova in a fourth round clash later on Monday.
