Abraham Ancer putts on the 18th green during the second playoff hole in the final round of the FedEx St. Jude Invitational on Sunday in Memphis, Tennessee. Photo: AFP

Mexico's Abraham Ancer birdied the second playoff hole to win the World Golf Championships St. Jude Invitational on Sunday, denying Hideki Matsuyama and Sam Burns for his first US PGA Tour title.

It was an unlikely trio in the playoff at TPC Southwind in Memphis, Tennessee, where overnight leader Harris English - two-up with nine to play - had two double-bogeys on the back nine and last-group playing partner Bryson DeChambeau was six-over on the back nine to fall out of contention.

"This is surreal," said Ancer, who carded a two-under-par 68 that featured three birdies and a bogey to finish on 16-under 264.

"I felt I left so many shots out there on the back nine, but you never know."

Masters champion Matsuyama - coming off a bitterly disappointing failure to medal at the Tokyo Olympics - charged into the playoff with a bogey-free seven-under-par 63 and Burns had eight birdies in his six-under 64 to make the playoff.

All three parred the first playoff hole, where Matsuyama watched his 18-foot birdie attempt burn the edge.

They returned to play the 18th one more time, Matsuyama again leaving himself a long birdie try that he couldn't convert.

Ancer stuck his approach six feet from the pin and Burns's approach settled just inside that.

After Ancer drained his birdie putt, Burns stepped up, but his birdie try circled the cup and failed to fall, leaving Ancer to hoist the trophy.

"I went right at it, and the shot played ­perfectly in my mind and it came out just how I pictured it," Ancer said of his bold ­approach into the second hole of sudden death.

The 30-year-old, who played college golf at the University of Oklahoma, claimed his first US PGA Tour title in his 121st career start - a run that has included four runner-up finishes.

English, who was trying to become the first wire-to-wire winner on the PGA Tour this season, finished alone in fourth on 265 after a three-over-par 73.

American Daniel Berger (66), England's Paul Casey (67) and Australian Cameron Smith (72) shared fifth on 266.

Smith was 16-under through 17 holes but made a double-bogey at the 72nd hole to fall out of the playoff. The Aussie hit into the crowd off the tee and tried to advance the ball through a narrow gap in the trees only to hit a branch.

"I wanted to make sure I had a good look at birdie and I just didn't execute it," Smith said.

DeChambeau, who started the day alongside Smith two shots off the lead, carded a four-over par 74 to finish tied with Will Zalatoris on 268.

"It's tough to lose in a playoff, but I wasn't able to hit the fairway with either tee shot," said Matsuyama, who was in the right rough off the tee on both playoff holes. "I want to congratulate Abraham, he played great all week."