HILTON HEAD, April 20, 2014 (AFP) - "I told my caddie before that last shot, 'I'm about due to make one of these,'" said Kuchar, who started the day four shots off Donald's 54-hole lead and fired a seven-under par 64 for an 11-under total of 273.
England's Donald carded a two-under 69 for 274. The former world number one now has five top-three finishes in this $5.8 million tournament in the past six years -- but no victories.
Americans Ben Martin and John Huh shared third place on 275. Martin closed with a 67 and Huh -- who was lying second, two strokes behind Donald, going into the round -- posted a final-round 68.
It was a further two shots back to Americans Scott Brown and Brian Stuard.
Kuchar was playing four groups ahead of Donald, but after the American's dramatic finish gave him a one-stroke lead the Englishman was unable to find a birdie in his remaining three holes.
At sixth in the world, Kuchar was the highest-ranked player in the field.
He claimed the seventh US PGA Tour title of his career and his first of the season, although he'd been knocking on the door in recent weeks with a tie for fourth at the Texas Open, a playoff loss to Aussie Matt Jones at the Houston Open and a tie for fifth last week at the Masters.
Things didn't look so promising, however, after Kuchar three-putted for bogey from inside five feet on the par-three 17th.
That had dropped him into a tie with Donald, after Kuchar had grabbed the lead with seven birdies in his first 10 holes.
"It was just pretty disappointing. It felt like a two-shot swing," Kuchar said.
He was less disappointed to find himself in the bunker at 18.
"I knew it was a pretty easy up and down," he said, although it turned out to be even better. "It was so cool to see that thing disappear at the end."
Donald's front nine included a double-bogey six at the par-four sixth, but he countered that with three birdies on the front nine to keep himself in the hunt.
Donald followed a bogey at 10 with back-to-back birdies, but couldn't find another birdie the rest of the way.
He had birdied the 17th in each of the first three rounds, but left himself a 28-foot putt and didn't make it.
At 18, his own chip slipped past the cup.
"I hit a lot of solid shots, a lot to build off and I'm excited about some of the changes I've been making," Donald said.
Scores after Sunday's final round of the $5.8 million US PGA Tour's Heritage (par 71, a-denotes amateur, USA unless noted):
273 - Matt Kuchar 66-73-70-64
274 - Luke Donald (ENG) 70-69-66-69
275 - Ben Martin 69-68-71-67, John Huh 71-68-68-68
277 - Scott Brown 70-69-71-67, Brian Stuard 69-72-68-68
278 - Brian Harman 69-71-69-69, Jim Furyk 71-66-71-70
279 - William McGirt 66-76-71-66, Rory Sabbatini (RSA) 69-72-70-68, Russell Knox (SCO) 69-72-68-70
280 - Stuart Appleby (AUS) 73-73-67-67, Jordan Spieth 69-74-70-67, Matt Every 69-70-70-71, Jason Kokrak 71-73-66-70, Charl Schwartzel (RSA) 70-70-68-72, Nicholas Thompson 70-70-68-72
281 - Pat Perez 74-69-74-64, Paul Casey (ENG) 74-67-72-68, Ryo Ishikawa (JPN) 77-68-67-69, J.B. Holmes 72-71-69-69, Ted Potter 70-69-71-71
282 - Graeme McDowell (NIR) 71-69-72-70, Martin Kaymer (GER) 73-67-72-70, Robert Allenby (AUS) 69-72-70-71, a-Matthew Fitzpatrick (ENG) 71-71-69-71
283 - Camilo Villegas (COL) 72-71-73-67, Chris Kirk 71-72-71-69, Tim Herron 69-72-72-70, Geoff Ogilvy (AUS) 72-68-71-