Hideki Matsuyama struggled to keep pace with the low scoring at the Fukushima Open, where his 3-under-par 69 saw him sink into 25th place after Saturday's third round.
Matsuyama, who returned to Japan after the completion of the British Open on Monday, carded five birdies and two bogeys in the third round, only to fall seven strokes off the pace of South Korea's Song Young-han at 17-under 199. Matsuyama started the day four strokes out of the lead.
With the galleries growing each and every day, Matsuyama, who went to school at Tohoku Fukushi University in neighboring Miyagi Prefecture, was unable to deliver in the sweltering heat. The 23-year-old is playing in his first domestic event of the season.
"It's unfortunate but I was unable to play up to standards," said Matsuyama, who had to apply ice to his head for relief. "It felt like I was suffering from mild heatstroke. I was in a bit of a daze."
He added: "I'm going to need about 10 under (on Sunday), but if I can make shots like I did on the second round, and my putts fall, I'll have a chance."