Fourteen years after becoming the youngest winner on Japan's golf tour as a humble 15-year-old amateur, Ryo Ishikawa is on the verge of missing out on his dream of playing at the Olympics on home soil.

Only a very high finish at this week's U.S. Open can earn Ishikawa the second spot on the Japan team alongside Masters champion Hideki Matsuyama for the Olympic golf tournament at Kasumigaseki Golf Club.

"Right now I'm just focused on my own goal, which is just trying to do my best this week against the golf course," he told Reuters on Tuesday after a practice round at Torrey Pines.