Donald could have replaced Germany's Martin Kaymer as world number one
-12 B Snedeker (US) L Donald (Eng) -11 T Gainey (US) -10 T Herron (US) R Barnes (US) -8 N O'Hern (Aus), B Crane (US) P Perez (US) Selected others: -3 I Poulter (Eng) +1 G McDowell (NI)
England's Luke Donald narrowly missed the chance to become world number one after losing a sudden-death play-off to Brandt Snedeker at The Heritage.
The result means Englishman Lee Westwood reclaims the number one spot after winning the Indonesia Masters.
Both players finished the tournament on 12 under par but Snedeker snatched victory at the third play-off hole when Donald's chip lipped out at the 18th.
Snedeker had fired a seven-under-par 64, while Donald could only make a 70.
The 33-year-old Englishman went into Sunday's finale knowing that a victory in South Carolina would have seen him usurp Germany's Martin Kaymer as the top-ranked player.
But second place allowed Westwood to regain the position he first clinched in October, while Kaymer slips to second with Donald third.
"It was going to be some big rewards if I won," said Donald.
"But I'll try and find the positives from this week and move on.
"Number one is not the final goal," he added.
"It's a constant travel. You're constantly moving forward in this game. To be number one would be great, but it's not everything.
"It certainly would be a tick in the box and it would be something great to talk to the grandkids [about] in 30 years' time and say that you were the best in the world, but I still have a lot of chances to do that.
"There are a lot of people who have a chance to be number one right now. It's a fun time in golf.
"Obviously Tiger Woods dominated for a number of years and no one was close to him.
"But now it's a little bit more of a race, that's kind of fun for the spectators."
Snedeker had produced the outstanding performance of the final day, firing nine birdies in his round.
The 30-year-old, from Nashville, Tennessee, went round the front nine in 30 shots and, after dropping shots at 13 and 16, he holed a 15-footer at the 18th to briefly snatch the outright lead.
Donald, who had a one-shot lead going into Sunday's final round, picked up two shots in his first five holes but he dropped shots on the seventh and the 10th, where he missed from three feet.
Snedeker carded nine birdies to clinch his second PGA Tour title
But a superb birdie putt at the 13th took him back into a share of the lead.
The Englishman had a golden chance to regain the lead on the par-four 16th but a five-footer slid past the left-hand side of the hole.
Needing a par to force a play-off, Donald found a greenside bunker with his second shot on the 18th but a sublime shot rolled a foot past the hole, leaving him a simple tap-in to take the match to a play-off.
Both players hit stunning second shots into 18 and made birdies before the 17th was halved in par.
Playing the 18th again, Donald found a bunker with his second shot and could only splash out to the far edge of the green.
With Snedeker having tapped in for par, Donald had to hole the ensuing chip but his brilliant effort hit the back of the hole and bounced out to hand victory to the American.
"It's a storybook ending, to be playing Luke in a play-off," said Snedeker after winning his second PGA Tour title.
"To even have a chance to win was exciting to me. I didn't really have any expectations at all.
"I came out and just kind of everything clicked. I drove the ball fantastic and came up with a lot of birdie opportunities."
Earlier, defending champion Jim Furyk, playing alongside Donald in the final group, made two double bogeys in the last four holes to card a 76 and slide to five under.
American Tommy Gainey took third place on 11 under par, with his compatriots Tim Herron and Ricky Barnes in a share of fourth on 10 under.