PALM BEACH GARDENS, 2 Mar 2015 (AFP) - The 43-year-old Dubliner, a three-time major champion who has fallen to 297th in the world rankings, withstood a dramatic morning shootout for the $1.098 million (982,000 euro) top prize at the $6.1 million tournament.
"The last nine holes I felt like a different person," Harrington said. "I think I've found that mental edge I've been lacking the past couple of years. Hopefully this isn't an isolated win."
Harrington found the water at the par-3 17th in regulation for a double bogey but sank a tension-packed 15-foot birdie putt at the par-5 18th hole to force the playoff, matching Berger on six-under 274 over 72 holes.
Both began the playoff with pars at 18 and then at 17, Harrington put his 5-iron tee shot four feet from the cup while Berger found the water. That allowed the Irishman to two-putt for the title.
"I was pretty keen on my own form at different stages but I wasn't delivering," Harrington said. "Last week I found something in the mental game, which is what has been going wrong.
"I felt a lot better on the course. I came out this week and 50 percent of the time I was at peace with myself. My mindset is maybe I can do it better in the future."
Englishmen Ian Poulter and Paul Casey and Scotland's Russell Knox missed the playoff by a stroke, sharing third on 275, with Welshman Jamie Donaldson another shot adrift and England's Luke Donald joining Americans Jeff Overton, Jim Herman and Patrick Reed on 277.
Harrington won the 2007 and 2008 British Open and 2008 PGA Championship, the last of those being his most recent PGA victory, although he also won the Asian Tour's Indonesian Open last December.
Berger, whose father coached the 2012 US Olympic tennis squad and is helping guide the US Davis Cup team in Scotland this week, missed a 13-foot birdie putt on the first playoff hole for the win in only his 12th PGA start.
"That putt on 18 was the most nervous I've ever been," Berger said. "I played a great final round. I did the best I could but I couldn't quite win. It was a great learning experience."
Berger, who closed a final-round 64 with back-to-back birdies, would have been the youngest winner in the event's 43-year history and matched the second-best 18-hole victory comeback in PGA history at nine shots adrift had he managed to win.
- Poulter, Casey, Reed falter -
A major thunderstorm on Saturday pushed the finish to Monday morning, when sunny skies greeted players for a thilling back-nine title battle.
Harrington and Berger were not the only leaders to stumble down the stretch, with Poulter, Reed and Casey also faltering over the final holes.
Play resumed with Poulter and Casey on seven-under, Reed one stroke adrift and six others within four of the lead.
Poulter sank a 14-foot birdie putt at the par-4 eighth to start his day and when Casey made bogey at 11, Poulter made the turn leading by two.
But Poulter found water on his approach at 11 on the way to a double bogey and twice more at 14, sinking a 20-foot putt to salvage a triple bogey and end the nightmare.
"It's back to the drawing board," said Poulter. "If I hit a soft shot, I have a tendency of pushing it. Soft shots have gotten me into a lot of trouble this week.
"It's just bitterly disappointing (after I) put myself in the position I had. A couple loose shots has cost me this tournament. I've handed one away this week and it's going to hurt."
Casey made bogeys at 11 and 14 to stumble back and Reed followed a double bogey at 15 with bogeys at 16 and 17.
Leading scores on Monday after the final round of the weather-disrupted US PGA Tour Honda Classic (USA unless noted, par 70, Harrington wins with par on second playoff hole):
274 - Daniel Berger 68-71-71-64, Padraig Harrington (IRL) 67-66-71-70
275 - Paul Casey (ENG) 69-70-68-68, Russell Knox (SCO) 69-68-70-68, Ian Poulter (ENG) 71-64-66-74
276 - Jamie Donaldson (WAL) 68-71-71-66
277 - Jeff Overton 71-68-69-69, Jim Herman 65-72-71-69, Luke Donald (ENG) 69-67-74-67, Patrick Reed 67-67-70-73
278 - Joost Luiten (NED) 71-71-67-69, George McNeill 72-70-68-68, Rory Sabbatini (RSA) 68-75-69-66, Brendan Steele 66-69-71-72, Brian Harman 70-74-70-64
279 - Camilo Villegas (COL) 73-71-67-68
280 - Jason Dufner 71-69-70-70, John Huh 70-73-68-69, Daniel Summerhays 71-68-70-71, Phil Mickelson 71-67-69-73, Martin Flores 67-71-74-68
281 - Zac Blair 71-71-69-70, William McGirt 71-71-69-70, Steve Wheatcroft 74-70-69-68
282 - Sean O'Hair 70-71-71-70, Ryan Palmer 71-72-71-68, Brendon de Jonge (ZIM) 69-71-71-71, Ryo Ishikawa (JPN) 74-65-72-71, David Lingmerth (SWE) 68-75-70-69, Lee Westwood (ENG) 71-73-72-66