Joint overnight leader and world No.1 Jason Day had a season-worst eight-over 79 to fall nine shots behind frontrunner Luke Donald at the RBC Heritage.
Donald has a one-shot lead, sitting on seven under at the PGA event in South Carolina after a third round of two under on Saturday.
Day has won two of his past three PGA Tour events and figured to contend at Harbour Town.
Instead, the Australian made eight bogeys and a double bogey.
His round derailed on the par-4 third where his tee shot found water before he went on to make a double bogey.
"I knew something was up when my ball hit a tree and bounced 80 yards right into the hazard," Day told the Golf Channel.
"From there, I just got a couple of bad breaks.
"It's really tough to fight back after that ... just got to try and improve tomorrow and see how it goes."
Day attempted to take his poor play in stride, signing autographs for fans behind the 18th green.
After winning the Arnold Palmer Invitational and The WCG-Dell Match Play, finishing 10th at the Masters, Day said several times this week he was ready for a break - which the PGA Championship winner will get next week.
Jason Kokrak and Charley Hoffman have a share of second place, sitting one stroke from the lead on six under.
Kokrak shot a 68, and Hoffman bogeyed the closing lighthouse hole for a 71.
Now, Donald looks to end his hard-luck history at the Heritage where the Englishman has five top-three finishes without a win.
Donald was a stroke behind when the round started and quickly moved up with three birdies on his first eight holes to reach eight under.
He bogeyed the 13th and trailed Hoffman by a shot.
But Donald steadied his game with five straight pars over the windy back nine to get himself on top once more.
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