In US Open men's singles event, Swiss third seed Stan Wawrinka outlasted tiring former champion Juan Martin del Potro in four sets to advance to the semi-finals. Twice grand slam winner Wawrinka ended the rousing comeback effort by the Argentine with a 7-6, 4-6, 6-3, 6-2 win to close out Day 10 at the year's last grand slam.Wawrinka will next meet sixth seed Kei Nishikori of Japan who upset world number two Andy Murray in five sets in their quarter-final. Other men's semi-final will pit world number one Novak Djokovic against French 10th seed Gael Monfils.