Juan Martin del Potro overpowered Dominic Thiem in a five-set US Open epic to book a quarter-final showdown with five-time champion Roger Federer.The 24th seed from Argentina Del Potro claimed a heroic 1-6, 2-6, 6-1, 7-6 , 6-4 victory over the sixth-seeded Austrian. Del Potro earlier defeated Federer in the 2009 final for his only career Grand Slam title before his career was almost torpedoed by a succession of wrist surgeries.Meanwhile, the third – seed Federer eased into the last-eight with a 6-4, 6-2, 7-5 win over Philipp Kohlschreiber.The top – seed Rafael Nadal claimed his 50th win at the US Open and will meet Russian teenager Andrey Rublev in the quarter final.In the women's event, world number one Karolina Pliskova set-up a quarter-final date against America's CoCo Vandeweghe. Estonia's world number 418 Kaia Kanepi also reached the quarter-finals, just the second qualifier to make the last eight.