Final round leaderboard:
-16 T Clark (SA) -15 R Allenby (Aus) -14 L Glover (US) -12 D Love III (US), H Slocum (US), B Van Pelt (US), B Crane (US), L Westwood (Eng) Selected others: -11 F Molinari (Ita) -7 P Mickelson (US) -5 L Donald (Eng), G McDowell (NI), A Scott (Aus) -2 R Imada (Jpn) level S Garcia (Spn) +1 O Wilson (Eng) Retired: T Woods (US)
Clark celebrates his five-under-par 67 at the 18th
Tim Clark won the Players Championship by one shot from Robert Allenby as overnight leader Lee Westwood's challenge faltered on the back nine.
South African Clark overtook Westwood with his sixth birdie of the day at 12 on his way to a 67 and a two-shot lead on 16 at Sawgrass.
Westwood double-bogeyed the 17th to finish four back and joint fourth.
World number one Tiger Woods retired after seven holes of his final round because of a neck injury.
By then, the 34-year-old was out of the running after firing in two over for the day, leaving him on two under overall.
But few would have banked on Westwood to be out of the frame too when he made his way on to the 18th on the famous Florida course.
Having led the event from the second round, the 37-year-old looked set to land his first title in the United States since 1998.
Westwood remained in the hunt on the outward nine, having shot one under for the day, but it all went wrong for the Worksop player coming in.
He only managed a bogey on the 14th and arriving on the short 17th, Europe's top player needed a birdie-birdie finish to force a play-off.
But his hopes faded when he hit a wedge into the water and consequently double-bogeyed, which resulted in him dropping to joint fourth.
A top-three finish would have pushed Westwood up to world number three for the first time in his career.
Westwood, who also lost his lead to Phil Mickelson on the final day of the Masters, believed he played poorly during the tournament.
"I'm disappointed but it's not something I'm going to pull my hair out over," he said after missing out on golf's richest prize - £1.1m.
"If you don't play well you don't deserve to win and I just didn't play well over the weekend.
"As the course got harder you really needed to be on your game and I wasn't striking the ball solidly enough.
"You needed to hit more fairways, have more control of the ball and I just didn't have that."
Now I'm just another guy with a win
Clark, on the other hand, was delighted to have finally rid himself of the tag of bridesmaid, having never won on the US circuit in 205 career starts and having finished runner-up eight times.
The South African fired in a brilliant round that included five birdies in six holes between seven and 12.
"That's as good as I could have played," said the 2005 Scottish Open champion, who finished with 66-67 from seven behind Westwood at halfway. He set a Stadium Course record with the largest 36-hole comeback.
"Obviously I'm over the moon but no-one is going to talk to any more - now I'm just another guy with a win."
Clark, who jumps from 40th to 20th in the world rankings, added: "I'm hoping that this will give me that little extra confidence that I needed. This may just be what gets me started.
"I had the last two weeks off and didn't even hit balls I was playing so badly but I just found something that clicked."
Australian Robert Allenby, among the leaders from the first round, was unlucky not to come away with victory, narrowly missing an eagle attempt on the 16th and then an 11-foot birdie effort at the 17th.
US Open champion Lucas Glover covered the back nine in five under for a closing 70 and third place at 14 under.
Phil Mickelson, who would have replaced Woods as world number one with victory on Sunday, began the day five strokes off the pace and ended it nine adrift after battling to a 74.
"The course conditions were very difficult, exactly what I needed to be able to try to make a run at the leaders," said the 2007 champion. "Unfortunately I didn't take advantage of it."
Apart from Clark, Davis Love III was the only other player to break 70 in the final round, with his 68.