Updated

San Martin, CA (SportsNetwork.com) - Jimmy Walker rallied for his first PGA Tour victory on Sunday as he came from behind to win the Frys.com Open.

Walker closed with a 5-under 66 to end the tournament at 17-under-par 267. The victory came in his 188th PGA Tour start.

"I think it'll sink in after a while. I'm still feeling the adrenaline right now. It feels like a release right now, but it feels really good," Walker said.

Vijay Singh posted a 3-under 68 to grab second place at minus-15. That was Singh's best tour finish since taking second place at the 2011 Northern Trust Open.

Third-round leader Brooks Koepka stumbled to a 1-over 72 at CordeValle Golf Club. He was joined in third place at 14-under-par 270 by Kevin Na (64), Scott Brown (64) and Hideki Matsuyama (66).

George McNeill (71) and Brian Harman (65) shared seventh place at minus-13, while Will MacKenzie (69), Billy Hurley III (68) and Max Homa (69) were one shot back at 12-under-par 272.

Koepka led by two to start the final round and birdies at the second and sixth pushed his lead to four. He stumbled to bogeys at nine and 11 to fall into a share of the lead with Walker.

Walker, a three-time winner on the Web.com Tour, birdied the second and fourth before tripping to a bogey on No. 5. He was playing in the group ahead of Koepka and birdies at the eighth and ninth moved Walker to 15-under at the turn.

Koepka fell back to Walker with his bogey at 11, but rebounded with a 3-foot birdie putt on the 12th to regain the lead. Walker answered with a 30-foot birdie effort at No. 13.

Walker 2-putted for birdie on the par-5 15th to gain a 1-stroke lead. He parred the next two holes to remain on top of the leaderboard.

"I was swinging good, so I just kept saying let's keep hitting good shots and putting good. Everything felt like it was in control, so I just kept doing that and it worked out," Walker stated. "You really do feel the pressure. I hit a really good tee shot on 17, maybe a little too good, and I hit a good one down 18, and maybe lost a little focus on the second shot."

Koepka missed the green at 16 and failed to save par. He then found water at 17 and that led to another bogey, which dropped him three off the pace. He found the fairway off the tee at 18, but it was too late as that tee shot needed to go in to force a playoff.

Walker tapped in his 3-footer for par at the last, and that sealed the win.

"I wasn't good enough to play golf on tour when I was at 20 or 21 like these guys are. They're really good," said Walker, speaking of Matsuyama and Jordan Spieth. "I've gone through everything. I played on a lot of tours, I've won on a lot of tours, and this is the final stepping stone. It feels great. I wouldn't take back anything I've ever done or anything I've ever gone through to get here."

Singh quickly moved within one early as he birdied the first and third, but he dropped shots at seven and eight. He was back at 12-under and five behind Koepka at the time.

The World Golf Hall of Famer started his climb back up the leaderboard with a birdie on the ninth. Singh birdied the next par-5, No. 12. After four pars in a row, he birdied the 17th to get within two, but parred the last to end alone in second.

NOTES: Walker earned $900,000 for the win and an invite to the Masters among other things. That will be Walker's first trip to Augusta as a competitor ... This was the first event of the 2013-14 PGA Tour season ... Koepka was looking to become the first sponsor exemption to win on the PGA Tour since Lee Westwood at the 2010 St. Jude Classic ... Koepka and Homa earned spots in next week's Shriners Hospitals for Children Open field with their top-10 finishes ... Ryan Moore is slated to defend his title next week in Las Vegas.