Rickie Fowler, aiming to put a season of struggle behind him, fired a nine-under par 63 on Saturday to grab a two-stroke lead over Rory McIlroy in the CJ Cup in Las Vegas.
Fowler notched his best round in three years, firing nine birdies without a bogey at the Summit Club, which is hosting the tournament usually held in South Korea because of the coronavirus pandemic.
Fowler won the most recent of his five US PGA Tour titles at the 2019 Phoenix Open.
Last season he failed to qualify for the FedEx cup playoffs for the first time in his 11-year career and he came into the week ranked 128th in the world.
He will have his work cut out for him on Sunday with low scores abounding at the Summit, where McIlroy capped his bogey-free 10-under par 62 with a 21-foot eagle at the 18th.
He was looking forward to the challenge.
"I haven't been there a lot the last couple of years, so it's nice to be back in that position," Fowler said. "It's been a long time coming. It's been a long road, tough times. We're not done."
Northern Ireland's McIlroy was nine off the pace at the start of the round, but raced up the leaderboard with five birdies in a row from the third through the seventh holes.
He added a birdies at the ninth, 12th and 14th before his final flourish.
"I think on a course like this you're going to have stretches where you're going to play good golf and hit good shots and maybe just not hole the putts," McIlroy said.
"I played an eight-hole stretch yesterday in even par, I made eight pars in row. It was nice to finish with a birdie last night. Then today I played a stretch of golf, played nine holes in six-under and all of a sudden you feel a little better about yourself.
"The big thing is I've played the last two days keeping it in the short stuff and I haven't made any bogeys. That's huge."
McIlroy was one stroke in front of a Mexico's Abraham Ancer (63), Australian Adam Scott (67) and American Robert (65).
England's Tyrrell Hatton and American Keith Mitchell were tied a further stroke back on 199 and Australian Cameron Smith and England's Ian Poulter were tied on 200 -- making it eight players within five shots of Fowler's lead.
Overnight leader Mitchell, who started the day with a five-shot lead, had two early birdies, but came unstuck when errant tee shots at the eighth and ninth led to back-to-back double bogeys.
He carded a one-over par 73, pulling back a stroke with a 28-foot birdie putt at the 18th.
Not everyone could take advantage of the scoring opportunities on offer.
Three-time major winner Jordan Spieth played in the final group with Mitchell, but didn't make a birdie until the 15th hole. That put him even for the day on the way to an even par 72 that left him eight adrift.