Japan's Kei Nishikori made a second-round exit from the Western & Southern Open on Wednesday, losing in straight sets to former world No. 3 Stan Wawrinka.The 2016 U.S. Open champion from Switzerland showed his game is back on track following a prolonged absence with a knee injury that saw his ranking tumble to 263 in June.Wawrinka, 33, landed 60 percent of his first serves and lost just six of the 31 points in which he did so, allowing just one break in a 6-4, 6-4 win over 28-year-old Nishikori."At the start we saw the tennis I want to play, but midway through I gave up on hitting some ball…READ FULL ARTICLE