Nick Watney claimed a two stroke victory at the AT&T National in Pennsylvania as K J Choi's challenge stumbled in the closing holes.
Watney had entered the final round in a share of the lead with Rickie Fowler after posting a course record eight under par 62 yesterday, but he could not shake off the attentions of Korean Choi.
The pair were level at 12 under par playing the par four 15th, but Choi found the rough of the tee, hit a bunker with his second and fired his third through the back of the green and could not get down in fewer than six shots.
Choi hit back by getting a birdie on the 16th, but that feat was matched by Watney who parred the final two holes to secure a second victory of the season.
Australia's Robert Allenby had at one point looked set to haul himself into contention for the victory when his ace at the par three 14th moved him to nine under overall, just two shots behind Watney at that time.
But a bogey at the 15th sapped the momentum from his challenge as he finished in an eventual tie for sixth with Chris Stroud.
England's Justin Rose was the top European contender in a tie for 15th at four under par but compatriot Brian Davis ended on three over par after a closing 72.
Choi admitted his errors on 15 had been key.
He said: "When I tied him on the 14th hole, I knew that there was still a lot of holes to go, and I knew the remaining holes were more favourable to Nick Watney, and I knew the 15th hole would be a turning point.
"That was a key hole, and I missed it. So I think that was the turning point of the match.
"The tee shot is a very difficult tee shot. It's a very long distance. I tended to hit it on the right side on that hole this week, so when you hit it on the right side, the rough is very difficult, so you really don't have a chance if you miss the fairway there."