The highest ranked among them , No. 33 Borna Coric , 18 , ran into Rafael Nadal in the first round .
19 - year - old Hyeon Chung won his first match but lost to No. 5 Stan Wawrinka in the second round .
The highest ranked among them , No. 33 Borna Coric , 18 , ran into Rafael Nadal in the first round , and 19 - year - old Hyeon Chung won his first match but lost to No. 5 Stan Wawrinka in the second round .