Phil Mickelson finally broke par with a two-under-par 69, but finished 10 strokes behind winner Jyoti Randhawa of India after the Suntory Open final round on Sunday.
Overnight leader Randhawa became the first Indian to win on the Japanese tour, earning $170,000 after holding his nerve for a closing 69 to finish at eight-under 276 at Sobu Country Club near Tokyo.
"I was so nervous in the last few holes," said a teary-eyed Randhawa, who also received 1,000 bottles of Suntory beer from the tournament sponsors to help him celebrate.
"It is a great feeling to create history in Japan. I still can't believe it."
Mickelson, still winless this season, birdied three holes on the front nine and picked up another stroke at the 12th, but then blotted his scorecard with two dropped shots coming home to return a two-over 286 total.
The American, who has slipped to 10th in the world rankings from second at the end of 2002, struggled with the stamina-sapping humidity over the four days and failed to break par until the final round.
"It was very warm, yes. Usually it is much cooler in Tokyo. It was uncomfortable because it was so hot," said Mickelson, who has failed to win in 13 visits to Japan dating back to 1992.
"But I drove it better on the front side (first nine) and made some birdies. I tried very hard this week. It is a very difficult golf course and the fairways are very tight."
Mickelson, who failed a try-out for Triple-A baseball team the Toledo Mud Hens last month, has won 21 PGA Tour titles and is widely viewed as the best player never to have won a major.
"I have tried really hard to win my first major title. Hopefully, it will happen next year," said the 33-year-old left-hander, who has not won a major despite 17 top-10 finishes in 46 starts.
Randhawa, playing his first season in Japan, underlined his title credentials with a gutsy 71 in blustery conditions on Saturday.
He never looked troubled during his final round, carding three birdies and a lone bogey on the par-four 17th.
Australian Paul Sheehan fired a final-round 69 to claim the runner-up spot on six-under 278, while Hiroyuki Fujita was the top Japanese finisher a further two strokes adrift.
