The 21-year-old Huh parred all eight holes in the playoff that matched the second-longest in PGA Tour history.
“It’s amazing,” Huh said. “It’s my rookie year, especially, and playing in my fifth event on the PGA Tour. I just couldn’t put it in words. … It’s really hard to explain this. It’s major. I mean, it was my dream.”
Huh closed with 8-under-par 65 to match Allenby at 13-under 271 on the seaside El Camaleon course. Allenby had a two-stroke lead with a hole to play in regulation, but the 40-year-old drove into the trees on the right and made a double bogey.
“Obviously, disappointed, disappointed that I didn’t like hit 3-wood off 18 in regulation, like I should have,” Allenby said. “But that’s the way it goes. You make some mistakes sometimes, and that was a major one, obviously.
“I mean, I had this tournament in the bag, a two-shot lead with one hole to play and just played it like a rookie, pretty much.”
The playoff fell three holes short of the PGA Tour record of 11 set in the 1949 Motor City Open when Cary Middlecoff and Lloyd Mangrum were declared co-winners. The playoff was the fifth to go eight holes and first since the 1983 Phoenix Open.
Matt Every and Colt Knost shot 66 to tie for third, two strokes back.
LPGA TOUR: In Singapore, Angela Stanford won the HSBC Women’s Champions on the third playoff hole, her first victory since 2009 and her fifth on the Tour.
The 34-year-old Texan parred the last playoff hole, knocking off Jenny Shin and Na Yeon Choi and Shanshan Feng.
“It’s a big deal,” Stanford said. “I’m just thinking about home and everybody there.”
Stanford earned $210,000 for the victory.
Top-ranked Yani Tseng finished fifth.