The Venezuelan, whose last victory came on this weekend in 2017 at the Canadian Open, birdied six of his last eight holes to add to the two shots he picked up on the front nine and post a 15-under total.
"Just kind of makes you feel like you're doing the right thing and you've just got to keep working hard," Vegas said.
"I've just been getting lucky on the back nine and hitting some good shots and making some great putts.
"You have to hit your irons really well on the back nine here, which I've been able to do for the past three days."
On a day of low scoring, four of the top five carded 63s including 46-year-old Matt Kuchar, who played his final 14 holes in nine under to move into second place in the penultimate event of the regular season.
Maverick McNealy, looking for his first win, is in third to boost his chances of making the FedEx Cup play-offs starting next month, while Patrick Fishburn, the fourth player to shoot 63, is joint fourth with Sahith Theegala (66) on 12 under.
One further behind in a tie for fifth is Australian Cam Davis, who shot a six-under 65 to rise 23 places.
Cam Davis rose 23 spots to be tied fifth at the PGA tournament in Minnesota. (EPA PHOTO)
It was the consistent Davis's best round of the tournament after his opening 68, which was followed by a 69.
If Davis can pull out a victory, he would join four others as multi-time winners on tour this year.
The 29-year-old Sydneysider, who won the Rocket Mortgage Classic earlier this year, played flawless golf on Saturday.
He made six birdies, including three in a row starting on the 12th, without any blemishes on his card.
"I've got my head in a place that feels good right now," Davis said. "I just feel like I'm in a position right now where everything is going well, it's just a matter of continuing to do the things I'm doing."
England's Matt Wallace, who only made the cut by a shot, charged through the field to give himself an outside chance of a second PGA Tour win of the season.
Starting the day three under par, he began with three birdies in his first six holes and, after bouncing back from his only bogey at the 11th with an eagle at the next, he closed with three birdies in his last four holes for a round of 64, with his 10-under total pushing him into a share of ninth.
Overnight leader Taylor Pendrith did briefly extend his two-stroke lead, but three bogeys and a double in five holes from the seventh and a 73 dropped him to 10 under.
Australian Aaron Baddeley also took advantage of the good scoring conditions to post a four-under 67, to move into a tie for 23rd at seven under.
Baddeley's round included six birdies, including on the first and last holes, and two bogeys.
with Reuters
