NEW YORK – Well after midnight, Stan Wawrinka kept coming. There were the usual one-handed backhand rockets—Wawrinka’s signature shot and one of the most lethal strokes in tennis—but the Swiss star also found success with finesse, mixing in timely topspin lobs (over a 6’6” opponent) and well-timed forays to the net. Finally, at 1:20 a.m. ET on Thursday, on a beautiful backhand down the line, Wawrinka extinguished the uplifting run of Juan Martin del Potro, who won the crowd but lost the match in four sets.
Despite being a No. 3 seed, Wawrinka is an unexpected semifinalist at the U.