Lee Westwood saw his 11-stroke lead at the Thailand Golf Championship reduced to four shots after a one-over-par 73.
The world number three, whose 64 in round two gave him a share of the Asian Tour's lowest-ever 36-hole total, struggled in the windy conditions.
"I hit a few good shots but I didn't make putts when I needed to, it was one of those days." he said.
South Africa's Charl Schwartzel is four shots back after shooting a 66.
Westwood believes he still has the upper hand on the field, and that the pressure is on his rivals to overhaul his lead and deny him his third Asian victory this year.
"A lot of people are going to think you're going to shoot a 60, 62 and 64 every day but I'm afraid golf isn't like that," added the 38-year-old from Worksop.
"It was one of those days, a few bad breaks, but if you'd have offered me a four-shot lead on Thursday morning I'd have taken it."
It might have been an even better day for US Masters champion Schwartzel, but he bogeyed the par-four 18th - his only dropped shot of the round.
American Michael Thompson stands three shots behind Schwartzel in third place on the leaderboard after his 69, with Dutchman Guido van der Valk two shots further back on 10 under.