Patrick Reed pumps his fist to celebrate his victory in the final round of the World Golf Championships-Mexico Championship on Sunday in Mexico City. Photo: VCG

Patrick Reed came through in the clutch, firing three late birdies in a four-under-par 67 for a one-shot victory over Bryson DeChambeau in the WGC Mexico Championship on Sunday.

Former Masters champion Reed stayed patient through a frustrating front nine at Chapultepec Golf Club, and as a string of leaders fell away powered to the victory with an 18-under par total of 266.

Birdies at the 15th, 16th and 17th pushed him to 19-under for the tournament, giving him a two-stroke lead.

The cushion proved enough after he pushed his tee shot at 18 well right but limited the damage to a bogey for the narrow win.

"It's very rewarding," said Reed, whose only other WGC title came in the same event in 2014, when it was played at Doral in Florida.

"To come back and win my second World Golf Championship - especially with how I had to finish on basically 15 onwards. The last hole was ugly, but it was what I needed to get the job done."

DeChambeau looked in control after five birdies in a six-hole stretch, his 14-footer at 14 putting him atop the leaderboard at 18-under.

But a three-putt bogey at the par-three 17th proved too much to overcome as he settled for a six-under-par 65 and a 17-under total of 267.

Justin Thomas, who took a one-shot lead into the final round, faded early on the way to a two-over-par 73 that left him tied for sixth.

Spain's Jon Rahm, who could have become number one in the world with a victory, briefly seized a share of the lead thanks to birdies at four of his first five holes.

But two birdies and two bogeys coming in weren't enough for the Spaniard, who shared third on 269 with South Africa's Erik van Rooyen, one stroke in front of world number one Rory McIlroy.

Reed was nowhere near matching Rahm's hot start. He got up and down for birdie from a bunker at the first, then parred his next 10.

"It definitely tested me today," Reed said. 

"The birdie barrages that were happening, it seemed like I was having to get up and down at every hole on the front nine. I think I only hit three greens on the front nine."

He began to gain ground with a tap-in birdie at the 12th, and made another from less than three feet at 15. Another short birdie at 16 was followed by a tough 17-footer at the 17th.

Reed's perseverence will pay off with a rise to eighth in the world.

The satisfying victory capped a week in which Reed again found himself criticized - this time by compatriot Brooks Koepka - for an incident at the Hero World Challenge in December when video showed him moving sand behind his ball in a waste area.

He accepted a two-stroke penalty and although he denied intentionally trying to improve his lie, Reed hasn't been dogged by the affair all year.

"If you play the game, you understand the rules," Koepka told a radio interviewer on Monday when asked about it. "You understand the integrity that goes on. I mean, there's no room for it."

Reed said Saturday he was just trying to concentrate on his game.

"At the end of the day, you can't listen to what other people are saying," he said. 

"All you can control is what you do."