MEXICO CITY (AFP) — American rookie Jake Knapp captured his first PGA Tour title in only his ninth series start, outdueling Finland's Sami Valimaki down the back nine Sunday to win the Mexico Open.

The 29-year-old former nightclub bouncer from California squandered a four-stroke lead on the front nine but ground out victory on the back nine at Vidanta in Puerto Vallarta.

Knapp hit only two fairways in firing a level-par 71 final round to finish 72 holes on 19-under 265 and defeat Valimaki by two strokes after the Finn fired a closing 69.

"Didn't necessarily have my best stuff today, that's for sure," Knapp said.

"Knew it was going to be nerve-wracking. Knew it was going to be tough."

"It would have been nice to hit the driver better and hit it a little bit better, but I was super-pumped on how I played the finishing stretch. Just grinded it out."

Valimaki, making only his 11th PGA start, failed to become the first Finnish player to capture a PGA title.

Taiwan's C.T. Pan, Germany's Stephan Jaeger and American Justin Lower shared third on 270 with American Patrick Rodgers and Scotsman Robert MacIntyre another strokes adrift.

Knapp, ranked 101st, became the third rookie to win this season, matching the total for all of last season.

At the par-5 14th, Knapp pitched to just outside two feet and tapped in for birdie to reach 19-under, stretching his lead to two strokes.

Knapp made pars to keep that edge to the par-5 18th, where he found a fairway bunker but landed his third shot 12 feet from the hole and two-putted to seal victory.

"He kept it going on the back nine so I feel like I didn't lose it," Valimaki said.

"I played solid. It was a tough grind."

Knapp's thoughts were upon his late grandfather, who inspired him to play golf before dying last year of cancer.