Nadal through to semis in straight sets while Andreescu battles back to see off Mertens in New York

Diego Schwartzman may have been the smallest player in 25 years to reach the U.S. Open quarter-finals but gave Rafa Nadal a big fight and forced the Spaniard to grind out a 6-4 7-5 6-2 win on Wednesday to reach the last four at Flushing Meadows.