Rory McIlroy turned a potential eagle chance into a five-putt double bogey during the second round of the Pebble Beach Pro-Am in California.
The Northern Irishman, who started four shots off the lead, dropped down the leaderboard after carding a three-over-par 74 to leave him one-under overall.
The 28-year-old, whose partner this week is father Gerry, hit four more bogeys during an inconsistent round.
Americans Dustin Johnson and Beau Hossler share the lead on 12 under.
Englishman Paul Casey carded a two-under 70 to leave him on seven under after the two rounds, while Scotland's Russell Knox also went round in 70, after an opening round of 71.
America's Phil Mickelson, who has been playing with McIlroy at the event, which is held on three courses - Monterey Peninsula, Spyglass and the host Pebble Beach - is three shots off the lead after an impressive 65 on day two.
McIlroy, who started on the back nine, finished just short of the green with his tee shot on the par-four fifth hole before electing to putt form distance.
The eagle attempt ran six feet long, before another miss on the birdie shot.
He decided against re-marking his ball before his next attempt - for the par - ended even further away.
It took another two putts - making it a total of four from inside six feet - to make the double-bogey.