Craig Lee fired a 69 to lead by two entering the final round of the Abu Dhabi Championship, as Rory McIlroy was left to rue a two-shot penalty.
It appeared that McIlroy had carded a 68 to take him within one of the lead but it emerged that a drop he had taken from a spectator crossing on the second hole had been questioned and was under scrutiny.
After looking at the area from where McIlroy had played his shot, it was determined that his left foot would have been on the white line denoting the crossing.
That meant he had not taken full relief and a two-shot penalty was applied to his score, turning a par into a double bogey and a 68 into a 70. At nine under overall, he now trails Lee by three shots heading into the final round.
"I'm going to go and hit the gym so hard," a clearly frustrated McIlroy said. "I'm going to run myself into the ground to try to get some of the frustration out.
"There are a lot of stupid rules in golf and this is one of them."
Lee reached 12 under par with birdies at the 10th and 13th and although he dropped his second shot of the day the 16th he got it straight back at the next.
The Scot, whose best finish on the Tour came when he lost a play-off to Thomas Bjorn for the Omega European Masters last September, is relishing being in contention again.
"It's exciting," said the 36-year-old. "The quality of the players behind me is nothing I have been used to before.
"I can't control what they are going to do, I just have to go out and play the best I can. I can look back on last year when Jamie Donaldson won (holding off the likes of Justin Rose) and say it's possible and fairytales do happen."
Phil Mickelson had set the clubhouse target four hours earlier when he returned a 63 after only making the cut with a shot in hand.
The American gave himself an outside chance of posting the first 59 in European Tour history after following up a front-nine 31 with further birdies at 10, 11 and 13.
A bogey at 14 effectively ended his bid for a place in the record books, but he picked up another shot at 15 and closed with another birdie despite carving his approach from a fairway bunker into a sandy waste area.
The American shares second place following McIlroy's demotion with Indian Gaganjeet Bhullar, who shot a bogey-free 66, while the Northern Irishman is one further back alongside Pablo Larrazabal of Spain, who returned a 68.
Joint overnight leader Rafael Cabrera-Bello slipped into a group of five on eight-under after a 73, rescued by his only birdies of the day at 17 and 18.