Wawrinka sets up quarter-final clash with del Potro

By Larry Fine NEW YORK (Reuters) - Double grand slam winner Stan Wawrinka set up a marquee quarter-final showdown with 2009 champion Juan Martin del Potro with a 6-4 6-1 6-7(5) 6-3 victory over Illya Marchenko of Ukraine at Flushing Meadows on Monday. Third seed Wawrinka, winner of the 2014 Australian Open and 2015 French Open, overpowered the 63rd-ranked Marchenko, who reached the fourth round when 14th-seeded Nick Kyrgios retired with a hip injury while trailing two sets to one. Marchenko was