Tony Finau never gave Masters champion Jon Rahm, or anyone else, much of a chance, closing with a bogey-free round of five-under 66 to earn a three-shot victory at the PGA Tour's Mexico Open.

Finau earned a small measure of redemption at Vallarta Vidanta, where last year he finished runner-up to Rahm by one shot.

Rahm had mounted a charge with a third-day 61 on Saturday but Finau maintained a two-shot lead going into the final round and was never seriously challenged once he got onto the back nine.

"Rahmbo is the best. I knew I was going to have my hands full to the end," said Finau, who finished at 24-under 260.

It turned out, though, that Rahm was not his biggest threat.

Brandon Wu, also a runner-up last year, holed a 45-foot eagle putt on the par-5 sixth hole and made a short birdie on the next to briefly tie for the lead.

Finau answered with a birdie on the seventh, before Wu fell back with a bogey from the bunker on No.8 and a tee shot into the water on the 10th that led to double bogey.

"Just a few too many loose swings," Wu said after a 68 to finish third.

"Satisfied with how I went today. I'm glad I gave myself a chance through nine holes."

Rahm closed with a 67 and certainly had his chances.

He was three behind Finau at the turn, but failed to birdie two of the par 5s with a poor drive on the 12th and a poor approach on the 14th.

"It was a day where I didn't do much wrong, but I didn't do much right, either," the world No.1 said.

Akshay Bhatia, the 21-year-old who has special temporary membership, faded to a 70 and finished fourth.

Finau now has two victories this season - his other came in the Houston Open - to join Rahm, Scottie Scheffler and Max Homa as the only multiple winners on tour this season.

Finau's sixth career PGA Tour victory was worth $US1,386,000 ($A2.1m). He also moved to No.11 in the world.

Rahm was playing for the second time in three weeks since winning the Masters.

He is skipping the Wells Fargo Championship - his one opt-out from elevated events with a $US20m purse - and will have a two-week break going into the PGA Championship.

Finau, who went more than five years between his first and second wins on the PGA Tour, now has multiple wins in back-to-back seasons.

"Obviously I wanted to win, but it's a reminder that everybody out here is a great player," Rahm said.

"Tony came out with a two-shot lead and played fantastic golf."

Australians Geoff Ogilvy and Aaron Baddeley shot final-round 70s to finish in a tie for 39th, while Cameron Percy was four shots further back at three-under overall to be equal 60th.