KAPALUA, 13 Jan 2015 (AFP) - Reed had holed out for eagle on the 16th to grab a share of the lead at 2-under par. After a bogey at 17 he birdied the par-five 18th at Kapalua's Plantation course regulation to complete a 67 for 21-under 271.
"I just stayed patient. That was the main thing all day, I just tried to stay patient and tried not get ahead of myself, tried not to make any careless errors," Reed said. "Luckily, I was able to hole a wedge shot on 16 to kind of get the momentum, but unfortunately I missed another short putt (at 17).
"Here on the last, I gave myself that chance and I was lucky enough to make it."
Walker, who came into the final round tied for the lead with Japan's Hideki Matsuyama, parred the final four holes en route to a 69 that also put him on 271.
The two returned to the tee on the 18th for the playoff.
Reed was in the right rough off the tee but hit a good second shot into the fairway.
Walker was in the fairway off the tee, but hit his second shot into a grandstand.
Reed chipped his third to 18 feet before Walker pitched his third over the green after taking a drop in the rough.
Walker chipped back to six feet, but never hit the putt after Reed drained his birdie attempt to seal his fourth PGA Tour title.
Walker, a three-time winner last season, had a three-shot lead with eight holes to play, and he missed a long birdie chance at the final hole of regulation that would have given him the win.
- Just didn't happen for Walker -
"It was there for me to take and it just didn't happen," said Walker, who will try to bounce back later this week when he defends his Sony Open title at Waialae Country Club in Honolulu.
Australia's Jason Day matched the course record as he fired an 11-under 62 in the final round.
Day shared third place on 272 with Russell Henley, who carded a 67, and Matsuyama, who closed with a three-under par 70.
South Korea's Bae Sang-Moon also posted a 70 and was lone in sixth on 274.
Last year's champion Zach Johnson fired a 67 to end in seventh on 275.
Chris Kirk also fired an 11-under 62 on Monday, like Day matching the course record that South Korea's K.J. Choi set in 2003 and Northern Ireland's Graeme McDowell matched in 2011.
Kirk finished with a share of 14th place on 279.
Masters champion Bubba Watson, the highest-ranked player in the field at fourth in the world, carded a 70 that left him six shots off the lead.
The $5.7 million tournament, limited to last season's tournament winners, was the first US PGA Tour stop of 2015 as the 2014-15 campaign resumed after a December break.
Leading final-round scores on Monday in the US PGA Tour Tournament of Champions (x-won at first playoff hole. USA unless noted, par-73):
271 - x-Patrick Reed 67-69-68-67, Jimmy Walker 67-68-67-69
272 - Jason Day (AUS) 70-69-71-62, Russell Henley 65-70-70-67, Hideki Matsuyama (JPN) 70-66-66-70
274 - Bae Sang-Moon (KOR) 66-69-69-70
275 - Zach Johnson 68-67-73-67
276 - Robert Streb 67-69-71-69, Brendon Todd 69-67-69-71
277 - Bubba Watson 70-69-68-70
278 - Noh Seung-Yul (KOR) 71-70-69-68, Ben Martin 67-72-70-69, Matt Jones (AUS) 69-72-68-69
279 - Chris Kirk 68-76-73-62, Charley Hoffman 70-66-73-70, Scott Stallings 67-70-70-72
280 - Brian Harman 70-70-75-65, Matt Kuchar 68-70-74-68, Hunter Mahan 71-71-69-69
281 - Chesson Hadley 70-73-68-70, Ryan Moore 71-70-69-71
282 - Steven Bowditch (AUS) 69-73-71-69, Billy Horschel 72-70-70-70, Kevin Streelman 69-73-67-73
283 - John Senden (AUS) 68-71-73-71, Tim Clark (RSA) 70-75-67-71
284 - Geoff Ogilvy (AUS) 72-69-74-69, Matt Every 73-71-70-70
286 - Angel Cabrera (ARG) 71-73-72-70, Ben Crane 74-67-73-72, Nick Taylor (CAN) 69-73-72-72
286 - Camilo Villegas (COL) 71-70-71-75
289 - J.B. Holmes 69-71-73-76
Kevin Stadler 74-73-WD