Japan's former world No. 4 Kei Nishikori revealed Sunday that his declining motivation due to mounting injuries lay behind his decision to draw the curtain on his career.The first Japanese player to advance to the final of a Grand Slam at the 2014 U.S. Open, Nishikori was attending a press conference for the first time since his announcement in late April that he is retiring at the end of the season."It crossed my mind for the first time (after a tournament last August)," the 36-year-old said. "I had pain in three, four parts of my body and I found myself unable to make up my mind to regain…READ FULL ARTICLE