England's Chris Wood leads by three shots going into Saturday's final day of the Qatar Masters in Doha.
The 25-year-old from Bristol shot a 64, which included an eagle and seven birdies, for a 15-under total
Former PGA champion Simon Khan, New Zealand's Michael Campbell and Sweden's Alex Noren are in joint second on 12 under.
Wood was fifth in the 2008 Open as an amateur before narrowly missing out on the play-off the following year.
The Englishman, the current world number 142, had started the day two shots behind the quartet of leaders, Ryder Cup stars Sergio Garcia and Martin Kaymer, Australia's Marcus Fraser and Ricardo Santos of Portugal.
But he took advantage as their challenges faded - Garcia and Kaymer managed only 70 and 72 respectively to be on 11 under and nine under with the Spaniard going in the water with his third shot to the par-five last and taking six while Fraser had a 71 and is on 10 under while Santos shot a 76 to drop to five under
The highlight of Wood's round was an eagle on the 548-yard 10th and having already notched up five birdies, an eight-foot putt lifted him clear of the field and there he stayed.
Although he is chasing his first European Tour victory Wood did capture the Thailand Open last August.