'It's nice to do it that way,' said Donald, referring to his comeback. 'Fortunately for me, the guys in the first two groups didn't play their best and let me have this one a little bit.'
Reigning U.S. Open champion Michael Campbell faced an 8-foot par putt on the 72nd hole to take third place by himself. He missed it, and it cost him $75,000 as Campbell tied for third with 2002 winner Padraig Harrington. The Irishman double-bogeyed the last to post a 73 and join Campbell at minus-12.
Tournament host and defending champion Tiger Woods never got on track this week. On Sunday, he struggled to a 1-over 73 and tied for 14th place in a 16-man field at minus-2.
Donald was 3-under par on his round through the first nine holes, and after back-to-back birdies from the 10th, found himself in the hunt. Clarke and Harrington were still the top-two, but Donald snuck to within three shots.
At the 13th, Donald, ranked 13th in the world, drained a 6-foot birdie putt to reach 14-under par and trail by two. Donald split the fairway at 14 and knocked his approach to 10 feet. He converted that birdie putt and inched one shot from the lead as Clarke parred every hole from the fifth.
Clarke almost fell from the top spot when his tee ball at the par-3 12th landed in the left bunker. His blast ran 35 feet past the stick, but the European Ryder Cupper rolled in the par save to stay in first.
He received company atop the leaderboard when Donald got to the par-5 16th. His second skidded through the green, but the man who celebrated his 28th birthday on Wednesday chipped to 10 feet and sank the birdie putt.
Clarke still had five holes to play with a chance to make birdie and go one ahead. He made routine pars at the 14th and 15th holes, and had a great look at the par-5 16th green with his second shot. Unfortunately, Clarke pulled his approach badly to the left and could not even reach the green with his third shot.
Clarke pitched 7 feet past the hole, but missed the par save to drop one behind Donald, who was on the range preparing for a possible playoff.
At the par-3 17th, Clarke's tee ball rolled 15 feet past the cup. He faced a delicate downhill, left-to-right birdie putt, but never gave it a chance. The ball came up almost 4 feet short and Clarke muttered aloud why he would leave it that short. He made the par-saver and still had a chance to force a playoff with a birdie at the last.
If Clarke was to birdie the closing hole at Sherwood, he would have been the first on Sunday. He got the first part down with a strong drive in the fairway, but pulled his approach 40 feet left of the pin. Clarke once again came up short with a birdie try, this time almost 15 feet, giving Donald the title. Clarke missed the par putt to lose by two, but Donald deserved the credit for his 64.
'This is the kind of course you can make a string of birdies,' admitted Donald, who posted two runner-up finishes this year on the PGA Tour. 'I played really solidly. I missed a few putts on the front side, so it could have been better.'
Donald collected his second win in the United States as he captured the 2002 Southern Farm Bureau Classic. He owns two European Tour victories and a title at the 2004 World Cup with Paul Casey.
This is not an official win on the PGA Tour for Donald, but the $1,300,000 first-place check is very official. A win like this can bring confidence to a player who should have more victories.
'This year has been a year of 'nearlys' up until now,' acknowledged Donald. 'Luckily I managed to win the last tournament of the year. I have always believed in myself.'
Kenny Perry shot a 72 and finished alone in fifth at minus-11. Tim Clark (69) and David Toms (66) shared sixth place at 9-under-par 279. Thomas Bjorn carded a 3-under 69 for eighth place at minus-8.
Fred Couples (73) and Jim Furyk (68) shared ninth at 6-under-par 282. Chris DiMarco (73) and David Howell (70) tied for 11th place at 5-under-par 283.
Fred Funk shot a 70 and came in 13th at minus-4. Woods shared 14th with Colin Montgomerie, who posted a 71 on Sunday. Davis Love III, a two-time winner of this event, only managed a 2-over 74 in the final round and came in 16th at plus-2.