Matt Every had four double bogeys in an 83 as the first-round leader of the Arnold Palmer Invitational saw his hopes of a third title at the event crumble to dust.
After an opening seven-under 65 put him one shot ahead of Rory McIlroy, Every's game fell apart in the second round at Bay Hill on Friday and he looked sure to miss the halfway cut.
His 11-over display included doubles at the fourth, 10th, 11th and 18th, a three putt from inside 18 feet at the last compounding his wretched day.
Every was repeatedly wayward and found water with his second shot at the par-four 11th on his way to a six.
American Every, 36, had overcome high winds on Thursday as one of the late starters, looking in good shape to mount a challenge at the tournament he won for the first time in 2014 and successfully defended a year later.
Thursday's performance defied recent form, given Every missed the cut at the Honda Classic a week ago after a second-round 85.
More Friday frustration left Every two shots outside the expected cut line as play continued, with England's Tyrrell Hatton nudging one shot clear of the field after 13 holes of his round, two under for the day and six under overall.
World number one McIlroy, champion in 2018, was battling to avoid a high score after a double-bogey six at the eighth, but he responded with a birdie to sit two back from Hatton.
Former rankings leader Jason Day withdrew from the tournament early in his second round, abandoning on the fifth hole due to a back injury.