NAPA, Calif. — Tyler Duncan may not sleep well and he'll likely be nervous. But it's understandable for the PGA Tour rookie and unlikely leader after three rounds of the Safeway Open.

Playing is his first tournament as a PGA Tour member, Duncan parred the 18th hole and scrambled to a 1-under 71 to maintain a one-stroke lead Saturday in the season-opening event.

"I feel OK now, but I'm not sure it's sunk in yet," said Duncan, whose only previous PGA Tour event was the 2015 U.S. Open as a sectional qualifier. "But it probably will after dinner when I'm laying in bed. I'm sure I'll be nervous tomorrow, but I am looking forward to it."

Duncan had five birdies and four bogeys to reach 14-under 202 at Silverado Resort and Spa. He hit his tee shot in the water on the par-3 15th hole en route to a bogey.

"The shot on 15 was probably the worst shot I've hit in a long time," Duncan said. "But I made a nice bogey and then made a nice par save on 18."

Chesson Hadley, a one-time PGA Tour winner who had a course-record 61 in the second round, was a stroke back after a 70.

"I was very pleased with my round," Hadley said. "I thought the course was playing very difficult and I didn't get off to a very good start. I was two over through four or five holes. But I hung in there and didn't panic."

Bud Cauley, winless in five PGA Tour seasons, shot a 66 to join defending champion Brendan Steele (72) at 12 under.

Phil Mickelson, seven shots behind Duncan entering the round after consecutive 69s, had a 68 and is 10 under.

Mickelson has seven consecutive rounds in the 60s in the event. He finished eighth last year and is seeking is first title since the 2013 British Open.

"Well, I am going to win, It's a matter of time," Mickelson said. "I don't know if it's tomorrow. I don't know if it's in China, but it's going to happen. It's going to happen soon because I'm starting to play well enough to do it."

DUNHILL LINKS: At St. Andrews, Scotland, defending champion Tyrrell Hatton opened up a five-shot lead heading into the final round of the Alfred Dunhill Links Championship.

A bogey-free 7-under-par 65 put Hatton in a commanding position to defend the title the Englishman won by four shots last year at St. Andrews, the home of golf.

After opening with a 68 on the Old Course on Thursday, he followed that with a 65 at Carnoustie, and matched that mark at Kingsbarns to go to 18 under.

Gregory Bourdy of France was his closest challenger at 13 under after a 66.

Paul Dunne of Ireland was at 11 under, with former world No. 1 Luke Donald and Ross Fisher a further shot back.

Rory McIlroy was at 4 under overall, one more than the cut line.

Hatton got up to 14th in the world rankings in March before enduring a frustrating summer, but that will all be forgotten should he become the first man to successfully defend this title.