Adam Scott on Sunday blew a chance to defend his Masters title as the world number one, receiving a harsh reminder of the capricious nature of golf and the importance of putting.

Scott frittered away a three-shot lead in the final round at the Arnold Palmer Invitational, making just one birdie in a four-over-par 76 as he plunged to finish third behind winner Matt Every at Bay Hill in Orlando.

Instead of overtaking Tiger Woods at the top of the rankings and heading to Augusta in a fortnight as a clear favorite, the 33-year-old Australian again faces questions about the apparent fragility of his putting.

"I'm annoyed I didn't putt at all well today," Scott, who also blew a four-shot lead in the final round at the Australian Open less than four months ago, told Golf Channel.

"I really think the putting is let me down on both those occasions.

"Today was a bit shaky. My short game just wasn't there, so that needs to tighten up. It probably shows I need to do a bit more work on it to hold up under the most pressure."

Scott scored worse each day, shooting 62 68 71 76.

He had a seven-shot halfway lead and seemed headed for a massive victory. A final round one-over 73 would have been enough to win.

Nobody has blown such a large 36-hole lead on the PGA Tour since Tom Weiskopf also led by seven strokes at the 1975 Westchester Classic.

Scott drove the ball with his customary aplomb on Sunday, with the notable exception of the par-four third, where he yanked his tee shot into the water, but his iron play was inconsistent and putter cold.

He sank only one putt longer than seven feet, and shockingly missed a three-footer at the par-five 16th that would have pulled him back within a shot of the lead.

If there is one positive, it is that he will not suffer from complacency heading to the April 10-13 Masters.

"Playing in contention was fun and I definitely identified a couple of areas I'll be working on the next couple of weeks," he said.

"It was good to be back in the mix again. If nothing else, it's a good reminder on how much putting practice I need to do going to the Masters and just how important it is.

"And if I think back to last year, I made every putt that you expect to in that last round and ultimately that's maybe what gave me the chance to win."