The 28-year-old from Sydney started Sunday's final round two strokes behind Sahith Theegala and eventually finished four shots behind the first-time winner at 17-under-par after shooting a two-under 70.

World No.37 Theegala earned his first PGA Tour title after a 68 left him two clear of South Korea's S.H. Kim, who also shot four-under in the final round.

The 25-year-old California native made a splash early in his pro career and qualified for the FedExCup Playoffs earlier this season, but a victory was missing from his resume until his exploits at Silverado Resort's North Course in Napa.

"It doesn't feel real," Theegala said on the Golf Channel broadcast.

"It's probably not going to set in for a while.

"That was some of the most fun I've ever had in my life."

World No.49 Davis was seeking to add to his breakthrough win on the Tour at the 2021 Rocket Mortgage Classic.

But a bogey on the par-4 4th and a double on the par-4 8th scuppered those hopes, though he did finish strongly on the back nine with an eagle and two birdies.

After going close as a rookie, Sahith Theegala claimed his first PGA Tour victory in impressive fashion in California. PHOTO: Orlando Ramirez/Getty Images.

"It was an awesome week. I really enjoyed everything about this week actually," Davis said.

"Just didn't quite get off to a really good start today which kind of threw me so far off that I wasn't really a contender anymore.

"It was awesome to watch how well Sahith played today. He did everything he needed to do to get the job done today."

Having led the tournament after a first round 63, Australian Lucas Herbert carded a 72 to be tied-30th at seven-under.

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After starting the day with a two-stroke lead, Theegala carded four birdies and one bogey on the front nine. His second dropped shot came at the par-4 10th, but he closed out the win with an 11-foot birdie putt at 12, a 20-foot birdie putt at 14 and a seven-foot birdie on 16.

That was plenty of cushion for him to absorb a bogey at the final hole, even after Kim finished with four birdies on the back nine.

"It was an awesome week. I really enjoyed everything about this week actually. Just didn't quite get off to a really good start today ..." – Cam Davis.

Eric Cole (70) was fourth at 16-under and fellow American Justin Thomas (72) placed fifth at 15-under, his highest finish since February.

Kim moved from 83rd to 57th in the standings of the inaugural FedExCup Fall series, which for the first time is using the seven events after the Tour Championship to finalise eligibility for next season.

The top-125 at the end of the northern autumn will retain their full PGA Tour cards. Being in the top-60 will qualify players into two signature events next winter, the AT&T Pebble Beach Pro-Am and the Genesis Invitational.