Teen sensation Ryo Ishikawa got off to a disappointing start in his defense of the Munsingwear Open KSB title on Thursday after carding a 6-over-par 78 in the first round.
Ishikawa sits 13 strokes behind Hideto Tanihara, who reeled off seven birdies in a bogey-free 65, and co-leader Nobuhito Sato. Masao Nakajima and Taichiro Kiyota shared third another shot back.
Ishikawa, who made history by becoming the youngest winner on the men's professional tour here last year, made two double bogeys through his first four holes and made the turn at 5-over after a bogey on the ninth at Tojigaoka Marine Hills Golf Club in Okayama Prefecture.
The 16-year-old continued to struggle on the back nine and dropped another shot on the 11th before double-bogeying the 13th. He regrouped to limit the damage with birdies on the 15th and 18th.
"I had three double bogeys and before I knew it I was at eight over," said Ishikawa, who missed the cut at last week's Japan PGA Championship.
"It's a very tough position to be in and I will have to play like a different golfer tomorrow. I will have to be a challenger again."
Shingo Katayama, riding high after a six-shot victory at the Japan PGA championship, had six birdies against a pair of bogeys en route to a 68.
Ishikawa won the title last year as an amateur at the tender age of 15 years and eight months, shattering the previous record of 20 years and seven months set by Seve Ballesteros at the 1977 Japan Open.
He also became the first teenager to win since the Japanese men's tour was established in 1973 and first amateur winner since Masahiro Kuramoto took the Chugoku-Shikoku Open title in 1980 at age 25.