However, Heath Slocum missed his 4-foot par putt that would have forced a playoff, so Calcavecchia collected his 13th PGA TOUR victory and first since the 2005 Canadian Open.
'I never expected him to miss that,' acknowledged Calcavecchia, who shot a final-round, 1-under 70 to finish at 10-under-par 274. 'I don't know what to say.'
Calcavecchia, armed with a one-shot lead over Slocum, hit a great drive on the 18th hole at the Copperhead Course at Westin Innisbrook Resort. Slocum found the short grass, but was farther back. Slocum knocked his approach to 27 feet, while Calcavecchia came up short with an iron from the fairway.
Calcavecchia chipped 5 feet short of the stick, but Slocum lagged his birdie try 3 feet short. Calcavecchia missed his par putt, but watched astonished as Slocum's par effort hit the left side of the cup and lipped out.
'I thought the first putt was going to be faster than it was,' said Slocum. 'The second putt I played the line I wanted. I made a good stroke. Just not enough break. It's done.'
'Heath did have a tough two-putt,' said Calcavecchia, who pocketed $954,000 for the win. 'You have to hit it hard enough to get it up the hill and if you do that, you risk putting it way by.'
Lucas Glover and Brian Gay each carded rounds of 2-under 69 and shared fourth place at 8-under-par 276. K.J. Choi, the 2006 champion, struggled to a 1-over 72 and tied for sixth place with FedEx Cup leader Charles Howell III, who fired a 6-under 65. The pair finished at minus-7.
Calcavecchia looked in control early as he tapped in a short birdie putt at the second and ran home a 10-footer for birdie at the sixth. Slocum double-bogeyed the second and appeared to be out of it, but around the turn, things tightened.
Calcavecchia missed the green at the par-3 eighth and made bogey. Slocum dropped a shot at nine, then Calcavecchia hit an errant drive en route to a bogey at the 10th.
Slocum birdied 10 and 11, while Calcavecchia also recorded a birdie at the 11th. Slocum drained a 25-foot birdie putt at the 12th to get within one of Calcavecchia's lead.
Calcavecchia hit a 7-iron to the back fringe at the 13th, but holed the long birdie putt to move two clear. He sank another long birdie putt at 14, but Slocum matched him with a birdie of his own. At the 15th, Calcavecchia stuck his tee shot 3 feet from the hole, but missed the short birdie putt.
Perhaps thoughts of the hole prior crept in Calcavecchia's head as he missed the fairway with his tee ball at the 16th. He had to pitch back into the fairway and hit his third shot to the back fringe. His 23-foot par save stayed above ground, so the lead was back down to one.
Slocum had a good look at birdie at 17, but did not convert. Then it was the hiccup at the last as Slocum was trying for his third win on the PGA TOUR.
Instead it was Calcavecchia in the winner's circle.
'It was all over the place,' Calcavecchia said about his mindset down the stretch. 'I went from being pretty good to in a matter of minutes, it was a tournament again.'
Jonathan Byrd (68), J.B. Holmes (69), Stephen Leaney (70) and Ryan Moore (70) tied for eighth place at 6-under-par 278.