Morikawa carved up Albany Golf Club to build a five-shot lead Saturday over Brooks Koepka, and too many pursuers faded from contention with a series of mistakes that only made another victory look inevitable for Morikawa.
With an 8-under 64 -- the first bogey-free round of the week -- Morikawa took a big step toward reaching No. 1 in the world.
"You love being in these spots and you don't get them every week," Morikawa said. "You wish you did. But when you do, you want to take advantage of them. So hopefully, we can take advantage tomorrow."
Morikawa chipped in for eagle on the par-5 third hole. His 10-foot birdie putt on the ninth hole gave him the lead. And then he shifted into another gear with a series of smart shots he executed flawlessly, a few par putts to keep momentum and par save from the bunker on the final hole to keep his distance.
Koepka fell back with a soft chip that didn't get up the hill on the par-3 eighth and led to double bogey. He was bogey-free the rest of the way for a 69 that at least got him into the final group.
"Just keep doing what I'm doing, play good and hope for the best," Koepka said.
Morikawa would stay at the top of the ranking with a victory, but only for only a week based on the two-year rolling formula. Even so, only 24 other players have reached No. 1 since the ranking began in 1986.
Morikawa was at 18-under 198 as he tries to win his second straight start. He is coming off a Sunday rally in Dubai to win the DP World Tour Championship, making him the first American to be the No. 1 player on the European Tour.
"It's not like I'm playing crazy or I'm playing stupid," he said. "I'm playing to my strengths and that's what I have to stick with. I'm going to keep doing what I do and if I don't feel comfortable on a tee shot, maybe play back, but overall I feel really good about the game so far."
Not long after Morikawa finished the opening hole in the final group, a dozen or so spectators lingered behind and headed to the back of Albany's practice range to watch someone who is not part of the 20-man field: Woods.
He spent another day hitting balls, this time with a driver, fueling speculation that 10 months after his car crash that badly damaged his right leg, he might tee it up in two weeks at the PNC Championship with 12-year-old son Charlie.
Tournament organizers are holding a spot in the field for him.
Woods wasn't quite ready to commit to that, and a return to the PGA Tour remained just as uncertain as when he spoke to the media earlier in the week.
"I can hit it," he said in the NBC booth during the tournament. "It just doesn't go very far." Leaning on another joke, he said he's not hitting it so short that "I can hear it land."
But he said he has a lot of work to do on his health, and playing against the best in golf remained a long way off.
Bryson DeChambeau started the third round with a one-shot lead and that was gone quickly. He hit a spectator at the back of the green, a good break for him when it caromed back and rolled off a slope onto the putting surface about 15 feet. And then he three-putted for bogey.
He shot 73 and now is eight shots behind.
Sam Burns made a big run with an eagle on the par-5 11th followed by four straight birdies to get within two shots of Morikawa. But he took bogey on the par-3 17th and finished his round with a double bogey for a 68 that left him six behind.
Daniel Berger recovered from a lost ball and double bogey on the par-5 third hole by making two eagles, only to drop two shots on the last three holes, including a tee shot in the water hazard on the 18th. He had a 69, also six behind.
Rory McIlroy, who began the holiday event with a share of the lead, never had a chance to get into contention after taking a quadruple-bogey 9 on the 11th hole. He had a 75.
The only other round over par belonged to Jordan Spieth, playing for the first time since becoming a father. His ball moved on the 18th green, and he forgot to replace it, leading to a two-shot penalty and a 75.