Luke Donald's bid to be the first man to win the PGA and European money lists in the same year faded further at the Disney Classic with a third round 70.
The world number one had five birdies but also a double bogey and a bogey and lies five behind leaders Kevin Chappell and Justin Leonard, who are 14 under.
Donald must finish in the top two for a chance of overhauling money list leader Webb Simpson but remained tied 14th.
Simpson carded a second successive 69 and is one ahead of Donald at 10 under.
Donald began the PGA Tour's final event $363,029 behind in second place and, because of Simpson's high position thus far, could find himself having to win the tournament, with its top prize of $846,000, to overhaul the 26-year-old American.
The Englishman had put himself in fine shape when his approach to the par-three 12th finished two feet from the cup and set up his fourth birdie of the day, taking him to 11 under and into a share of fourth place.
But taking a three-wood off the tee for placement at the par-five 14th he pushed his drive into the water on the right and compounded the error by three-putting for a seven.
Another uncharacteristically wayward tee shot veered into the trees down the left at the 16th and resulted in a further dropped shot.
Donald finished with a birdie after pitching to eight feet at the last but will need something miraculous in Sunday's final round, when for the third successive day he will play alongside Simpson.
"We're both trying to do the same thing, win the golf tournament," Simpson said. "It's been good to play with him.
"There's been a little added pressure but I think we've both handled it okay."
Chappell, seeking his first PGA Tour victory, began with a dropped shot but had seven birdies in a 66.
Leonard, the 1997 Open champion, had an eventful round of 70, chipping in from 70 feet at the fifth, using the sole plate of his wedge to roll in from off the green at the eight and holing out again at the next, this time with a chip from 35 yards.
"The strength of my round was definitely from off the green," he said, smiling. "I certainly didn't play great and to be able to hole the shots from off the green certainly is a huge boost.
"There are days when those things don't go our way, and the round can get away from me. Today I scored, and it's something I have not been doing at all this entire year."