Swiss third seed Stan Wawrinka outlasted tiring former champion Juan Martin del Potro in four sets to advance to the semi-finals of the US Open on Wednesday.

Two-time grand slam winner Wawrinka ended the rousing comeback effort by the Argentinean at Flushing Meadows with a 7-6 (7/5) 4-6 6-3 6-2 win to close out Day 10 at the year’s last grand slam.

Del Potro, the 2009 winner, had missed nine successive grand slams due to a string of wrist surgeries before returning to Wimbledon, where he ousted Wawrinka in the second round and went on to claim silver at the Rio de Janeiro Olympic Games.