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.