Hideki Matsuyama suffered a setback on Friday with an even-par 72 second round that saw him fall from second place to 14th at the Japan Golf Tour Championship.
The 21-year-old leader of this season's JGTO money rankings had a two-birdie, two-bogey round that left him at 5-under-par 139.
"Neither my shots nor my putts were any good today," said Matsuyama, who finished in a tie for 10th at last week's U.S. Open. "My concentration was very poor from the start. It's not fatigue. It's not even jet lag. I don't know what it is."
Playing in the same group with Matsuyama, U.S. tour regular Ryo Ishikawa began the day in last place and rebounded with eight birdies and a bogey but still failed to make the cut, finishing at 1-over par.
South Korea's Park Eun-shin seized the second-round lead with a spotless eight-birdie round of 64 and a two-day 133 total and a one-stroke lead over Satoshi Kodaira, who also shot a 64 at Shishido Hills Country Club.
S.K. Ho of South Korea (68) was in third another stroke back, while his countryman Park Sung-joon and Hiroyuki Fujita each carded a 67 to share fourth at 8-under-par 136.
