Hideki Matsuyama saved his worst till last as a bogey at the 18th in gusty conditions shaved his Zozo Championship lead to just one shot on Saturday.
The US Masters champion, who had been in control of the PGA Tour event all day at Accordia Golf Narashino Country Club, outside Tokyo, came to the final hole in his third round at 11-under par with a three-shot cushion over American Cameron Tringale.
But with a three-wood in hand, Matsuyama carved his tee shot so far left into the trees at the par-five closing hole - rated the easiest on the course - that he was forced to play his second up the adjacent ninth fairway.
His approach from 140 yards back over the trees landed short and he failed to get up and down, the bogey six resulting in a second consecutive 68 to go with his opening stunning round of six-under 64.
Playing partner Tringale, who is seeking his maiden PGA Tour win, was meanwhile taking the conventional route.
Although his second shot from the correct fairway came up just short, he chipped close enough to secure the birdie that took him also to a 68 and a nine-under par total, one behind Matsuyama.
Up until then, it had all been going smoothly for Matsuyama, Japan's first male major winner, who is seeking his seventh PGA Tour win and first in front of his adoring home fans.
The Japanese number one, having missed out on a playoff for an Olympic medal at the Tokyo Games just under three months ago, is desperate to make amends this week.
Two years ago, he pushed Tiger Woods all the way at the inaugural Zozo Championship on the same course as the 15-time major winner bagged a record-equalling 82nd PGA Tour win having led from gun to tape.
'Really tricky out there'
Followed by the majority of the 5 000 spectators a day allowed on to the course, Matsuyama was quickly into his stride.
Starting the day at eight-under par, he grabbed his first birdie at the par-four second and by the turn had moved to 10-under and extended his lead over Tringale to three shots.
Tringale birdied the 11th but Matsuyama hit back at the 16th to restore the three-stroke margin before the drama at the last.
"It was really tricky out there with the wind and fast greens," said the 34-year-old Tringale.
Englishman Matt Wallace, also playing in the final group, struggled for consistency in the breezy conditions and a disastrous bogey at 14, where he overcooked a slippery downhill putt and saw it run off the green, left him on six-under after a level-par 70.
"Just need a few bits to go my way," said Wallace, who is four behind going into the final round. "Just one after the other today and I just couldn't get it going. It happens."
He was joined on that mark in a share of third place by Colombia's Sebastian Munoz and American Brendan Steele who had a level-par 70.
"Wind got really nasty out there," said Steele. "This course is so narrow that you really have to be hitting good shots or you're struggling all day."
Munoz sprayed it around the course in a wildly entertaining round of 68 that saw six birdies, four bogeys and eight pars and admitted it was a round that could easily have gotten away from him.
World number three Collin Morikawa moved into the top 10 after an outrageous chip-in for eagle at the 18th gave him a round of 67.
He lies one behind South Africa's Branden Grace, who also carded 67, and Tommy Fleetwood of England who, try as he might, could not get a putt to drop as he parred 14 holes in a row to finish with a 70.
Third-round scores on Saturday at the PGA Tour's Zozo Championship at the par-70 Accordia Golf Narashino Country Club in Chiba, Japan:
200 - Hideki Matsuyama (JPN) 64-68-68
201 - Cameron Tringale (USA) 67-66-68
204 - Brendan Steele (USA) 66-68-70, Sebastian Munoz (COL) 70-66-68, Matt Wallace (ENG) 65-69-70
205 - Tommy Fleetwood (ENG) 67-68-70, Branden Grace (RSA) 72-66-67
206 - Collin Morikawa (USA) 71-68-67
207 - James Hahn (USA) 68-69-70, Adam Schenk (USA) 67-72-68, Mackenzie Hughes (CAN) 70-68-69, Alexander Noren (SWE) 68-68-71
208 - Joaquin Niemann (CHI) 64-71-73, Luke List (USA) 69-69-70, Sam Ryder (USA) 68-71-69, Wyndham Clark (USA) 70-68-70, Tom Hoge (USA) 72-70-66, Chan Kim (USA) 72-66-70
209 - Lanto Griffin (USA) 69-67-73, Hiroshi Iwata (JPN) 63-73-73, Takumi Kanaya (JPN) 71-70-68, Ryuichi Oiwa (JPN) 71-70-68, Matt Jones (AUS) 67-69-73
210 - Tomoharu Otsuki (JPN) 70-71-69, Shugo Imahira (JPN) 72-72-66, Ryan Palmer (USA) 72-68-70, Adam Long (USA) 72-67-71, Harry Higgs (USA) 68-72-70, Chris Kirk (USA) 69-70-71, Keegan Bradley (USA) 70-71-69, Kim Si-woo (KOR) 69-70-71
211 - Lee Kyung-hoon (KOR) 70-69-72, Erik Van Rooyen (RSA) 69-69-73, Matthew NeSmith (USA) 70-72-69, Kramer Hickok (USA) 67-74-70
212 - Troy Merritt (USA) 68-68-76, Tyler McCumber (USA) 72-69-71, Xander Schauffele (USA) 70-74-68, Pat Perez (USA) 70-69-73, Rickie Fowler (USA) 70-71-71, Shaun Norris (RSA) 68-72-72, Satoshi Kodaira (JPN) 73-67-72, Keita Nakajima (JPN) 73-69-70, Jhonattan Vegas (VEN) 67-72-73
213 - Ryutaro Nagano (JPN) 71-71-71, Yuki Inamori (JPN) 69-71-73, Rikuya Hoshino (JPN) 69-72-72, Andrew Putnam (USA) 73-69-71, Bill Haas (USA) 71-72-70, Kyle Stanley (USA) 70-72-71, Charley Hoffman (USA) 71-72-70
214 - Maverick McNealy (USA) 73-69-72, Henrik Norlander (SWE) 71-72-71
216 - Brandon Hagy (USA) 70-74-72, Doug Ghim (USA) 71-71-74, Kazuki Higa (JPN) 73-75-68, Jinichiro Kozuma (JPN) 74-71-71, Ryosuke Kinoshita (JPN) 67-75-74
217 - Naoyuki Kataoka (JPN) 68-71-78, Naoto Nakanishi (JPN) 71-73-73, Roger Sloan (CAN) 72-74-71, Peter Malnati (USA) 75-69-73, Wesley Bryan (USA) 75-72-70, Kang Sung-hoon (KOR) 74-69-74, Scott Vincent (ZIM) 72-73-72
218 - Robert Streb (USA) 74-77-67, Will Zalatoris (USA) 69-76-73, Tomoyasu Sugiyama (JPN) 73-72-73
219 - Ryo Hisatsune (JPN) 74-70-75, Emiliano Grillo (ARG) 74-70-75, C.T. Pan (TPE) 76-73-70
220 - Sepp Straka (AUT) 74-70-76, Garrick Higgo (RSA) 70-78-72
221 - Brendon Todd (USA) 72-78-71, Chesson Hadley (USA) 71-77-73, Ryuji Imada (JPN) 74-74-73
222 - Doc Redman (USA) 76-67-79
DNF: Carlos Ortiz (MEX)