Adam Scott produced an extraordinary fightback to win his second tournament in succession as Rory McIlroy squandered a four-shot lead in the WGC-Cadillac Championship.
Scott carded a closing 69 which featured two double bogeys in the space of three holes, a shank and seven birdies to finish 12 under par at Doral, one shot ahead of double Masters champion Bubba Watson.
England's Danny Willett was a shot off the lead before driving into the water on the 18th, the resulting bogey dropping him into a share of third with McIlroy, who struggled to a 74 featuring just one birdie.
It was the first time McIlroy had failed to convert a lead of three shots or more after 54 holes since collapsing to a closing 80 in the 2011 Masters.
Starting the day three shots behind McIlroy, Scott closed the gap with a birdie on the first before seemingly falling out of contention by finding water on the third and fifth to run up a pair of double bogeys as the Blue Monster course lived up to its name.
However, the 35-year-old bounced back with birdies on the sixth and eighth and started the back nine with three more in succession, before another on the 14th took him into a two-shot lead.
Willett and then Watson closed to within a shot with birdies on the 16th and 17th respectively, while Scott amazingly shanked a bunker shot on the short par-four 16th but crucially scrambled a par.
Scott's approach to the 18th was then just a few feet from finding the water to the left of the green, but the former Masters champion hit a superb chip to six feet and holed out for a dramatic victory.
Asked how he had pulled off his 13th PGA Tour title, Scott told Sky Sports: "I don't really know. This is such a wild golf course in conditions like the wind was today.
"I made a couple of horrible errors on the front nine but you can't give up hope and I thought if I can get a couple (of birdies) before the turn, maybe a great back nine is good enough if things go my way and they did somehow. It was messy and my golf wasn't that pretty today either.
"Somehow I started feeling a bit like I did last week and the swing came under control, the rhythm came back and I started hitting iron shots close, almost so close you couldn't miss them which was nice."
Scott won the Masters in 2013 using a long putter and reached the top of the world rankings in May 2014, but has successfully reverted to a conventional club in order to comply with the ban on anchored strokes which came into effect on 1 January.
"I have been working hard on my putting and couldn't ask for a better way to test myself, a six-footer to win a World Golf Championship event," he added.
"I can't believe I have won back to back weeks out here and to win a WGC is huge. Somehow I need to bottle this up and keep it another four or five weeks through the Masters and that would be amazing to get myself into contention there and have a chance."