But the 29-year-old American emerged from the pack with easygoing style, shooting a 66 on Monday to win the Puerto Rico Open by two strokes.
He finished at 19-under-par 269, setting a tournament record at Trump International Golf Club-Puerto Rico, a scenic palm-fringed 7,526-yard course which was deluged by rain early in the competition.
Kris Blanks shot a 69 and finished alone in second place at 271.
"I just kept on trying to make birdies, I kept on trying to be aggressive," said Lamely, who teed off on No. 10 in the final round, the first player to win in that position since Keith Clearwater at the 1987 Colonial Invitational.
The victory was worth $630,000 to Lamely, along with PGA playing privileges through 2012.
Holding up a crystal trophy, Lamely was thrilled even if the world's top-ranked players were on the U.S. mainland at the World Golf Championship stop, the CA Championships.
"I'm still a rookie out here, even though I just won. There's tons I can learn still," he said.
Lamely vaulted up the leaderboard during Sunday's third round by shooting a course record 9-under 63.
TOUR SPONSOR: Farmers Insurance must have liked what it saw at Torrey Pines in its 10 days as a title sponsor. It decided Monday to sign up for the next four years, filling an important hole of title sponsorship in the PGA Tour schedule.
PGA Tour commissioner Tim Finchem did not disclose financial terms, saying only that the purse next year would be $5.8 million, an increase of $500,000 from this year.
The PGA Tour now has 15 tournaments with title sponsor agreements through at least 2014, with 10 others signed through 2012.