Antalya - Masters champion Danny Willett slumped as Denmark's Thorbjorn Olesen hit a new course record 62 to open up a six-shot lead on day two of the Turkish Airlines Open on Friday.
Willett, who is looking to end the season as European number one for the first time, had hit an opening-round 69 but dropped back to a tie for 56th place after failing to record a single birdie in a three-over-par 74.
The English golfer arrived in Turkey lying second in the Race to Dubai and can regain the leading money list position by finishing fifth or higher in this week's 78-player field.
Olesen, 26, capped his round with an eagle along with eight birdies and just one bogey in a nine-under-par effort to move to a 15-under 127 total in ideal scoring conditions on the Regnun Carya resort course.
"I found something in my game playing the Portugal Masters and while I didn't score that well, I finished that week feeling like I was playing much better," said Olesen.
"So I was looking for something good to come and yesterday I produced a great putting display and today just played better and still putted great."
Olesen is chasing a fourth Tour victory and first in just over 12 months since capturing the 2015 Alfred Dunhill Links Championship in Scotland.
The Dane has contested 24 Tour events this year with his best finish a pair of second-place results at the BMW International Open in Germany and the Qatar Masters.
Olesen arrived in Turkey lying 38th on the European Tour's Race to Dubai and 92nd in the World Rankings. Victory would send the Dane to just outside the top-10 on the Race to Dubai.
Two players - Spain's Adrian Otaegui and Thailand's Thongchai Jaidee - share a distant second on nine under par.
Otaegui, 23, had set a new course record with an eight-under 63 but it lasted just over two hours before Olesen set a new low.
"I started with five consecutive birdies and from thereon I just tried to not think on anything, just tried to keep the momentum going," said Otaegui as he continues to chase a first Tour success.
Italy's Matteo Manassero, 23, showed a return to form with a 68 to move into a share of third alongside Swede Joakim Lagergren, England's David Horsey and China's Li Haotong.
The Italian had become the youngest winner on the European Tour in capturing the 2010 Castellon Masters.
He also became the first teenager to win three Tour titles while he won a fourth, his last victory, at the 2013 BMW PGA Championship.
First-round leader George Coetzee of South Africa slumped to a share of 13th place at five under par after putting two balls into the water in taking a quadruple bogey at his 10th hole in an eventual round of a two-over-par 73.