Former world number one Jordan Spieth, seeking a first victory in more than three years, fired a scintillating 61 at TPC Scottsdale on Saturday to share the Phoenix Open lead with Xander Schauffele.
Spieth had 10 birdies in his 10-under par 61, tying his career-low round on the US PGA Tour for an 18-under par three-round total of 195.
Overnight leader Schauffele fired a six-under par 65.
A victory would mark a return from the wilderness for Spieth, who won the 2015 Masters and US Open before his 22nd birthday but hasn't landed in the winner's circle since capturing his third major title at the 2017 British Open at Royal Birkdale.
"I have no expectations on the results tomorrow, I really don't," said Spieth, who has dropped to 92nd in the world amid his struggle to rebuild his game and regain his confidence.
"I built some freedom now seeing these results the first few days here to where I feel really good about the path I'm on.
"I feel good about what the long-term ahead looks like for me. And sometimes that has been in question, to myself."
Spieth finished in the top 25 in just four of his 17 PGA Tour starts in 2020 and last led or share the 54-hole lead in a tournament at the 2018 British Open -- when he was tied with Schauffele.
Spieth has had his troubles off the tee in the Arizona desert, hitting just 43% of fairways, but he has hit 80% of greens in regulation and on Saturday he made the most of his chances.
"To shoot 10-under, you've got to do a lot right, but I also got quite a few really good breaks," he said. "Each shot that ended up in the desert I think I ended up playing those holes two- or three-under today. You could easily end up in a cactus with an unplayable."
He followed four birdies on the front nine with back-to-back birdies at 10 and 11.
He was disappointed that he couldn't get a four-foot eagle putt to drop at 13 but tapped in for birdie.
- 'Really fun' -
Spieth two-putted from 25 feet for birdie at 15, then drained a 36-footer for birdie at the par-three 16th to roars from the crowd of 2,600 in the stands -- down from the 16,000 that usually pack into the hospitality suites around the hole but welcome nonetheless by players, who have missed the energy of fans during the coronavirus pandemic.
"The only downside of the birdie putt on 16 is that it would have been arguably the loudest roar I've ever had if it were last year," Spieth said. "But it was still loud. It is really fun."
Spieth added a 29-footer for his final birdie at 17.
Schauffele rebounded from a bogey at the second with three front nine birdies. He kept in touch with Spieth with birdies at the 13th, 14th and 15th, and regained a share of the lead with a seven-foot birdie at 17.
He, too, is trying to end a dry spell, having claimed the last of his four titles at the 2019 Tournament of Champions.
The leading duo have a three-shot lead over American Scottie Scheffler and South Korean Lee Kyoung-hoon, who both carded 66 for 198.
It was a further stroke back to former British Open champion Louis Oosthuizen and world number three Justin Thomas, who both carded 66 for 199.
Four-time major winner Brooks Koepka, coming off three straight missed cuts as he tries to get his 2021 campaign on track in the wake of a season hindered by injury as well as the pandemic, headed a group on 200 that also included James Hahn and Steve Stricker -- who at 53 is still in position to challenge Sam Snead's record for the oldest winner of a PGA Tour event.