Adam Scott was hoping to take another step towards his second European Tour title in the third round of the Qatar Masters.
Scott began the day with a three-stroke lead over the field thanks to a superb second-round 66 at Doha Golf Club.
The highlight of his round was an eagle two on the hardest hole on the course.
The 21-year-old Australian's 11-under-par total of 133 left him three clear of Spain's Jose Manuel Lara, Denmark's Anders Hansen and Swede Klas Eriksson, with Colin Montgomerie - his playing partner for the first two days - another shot back.
Scott had already carded three birdies and was tied for the lead when his drive on the 15th found the first cut of rough on the 466-yard par-four.
That left him a daunting 200-yard approach over water to the green, but what could easily have become a bogey five turned into an eagle two as his four-iron approach landed 25 feet short of the flag and rolled straight into the hole.
"Funnily enough, I was saying to my caddie just the other day that it's been five years since I've holed a full iron shot like that so I was due one I guess, and the 15th is probably the most difficult hole on the course," said Scott.
"Apart from that, I played beautifully on the front nine, the back nine wasn't so good but I hung in there and scrambled well.
"I'm delighted to be leading, I played really well in Dubai last week but struggled on the greens and I spent a lot of time working on my putting since then and it is starting to feel a lot more comfortable."
Scott, who famously shares both a coach, Butch Harmon, and a similar swing with world number one Tiger Woods, also birdied the 17th from 15 feet.
And the 2001 Alfred Dunhill Championship winner enjoyed a four-shot cushion over playing partner Montgomerie, a three-shot swing taking place on the 15th as Montgomerie made a bogey five to Scott's eagle from tee shots only a few yards apart.
"I can't control what other players are going to do over the weekend, but if I keep playing the way I have over the first couple of days then I think it will be good enough," added Scott, who secured his European Tour card in 2000 from just eight starts.
"I'll just keep my head down but I'm expecting the wind to come up now, so I presume it will get a lot more difficult over the weekend."
Darren Clarke leads the Irish at five under while while Des Smyth has slipped back to one under par.