British Open champion Louis Oosthuizen had his roughest ride for a week but the South African was still in the hunt for a Scandinavian Masters title to follow his major win, holding early second place after a 70.
The 27-year-old slipped five strokes off the second-round lead at one point on Friday but recovered gamely to trail front-runner K.J. Choi of Korea by two shots.
Choi set the halfway target with a five-under-par 67 which moved him to nine-under 135.
Oosthuizen lost ground badly just before reaching the turn, when he hit into the lake at the par-three 17th, his eighth hole, to run up a double-bogey.
That took Choi, playing a group ahead of him, five strokes in front after the Korean picked up an eagle and three birdies in five holes.
Both players had putting problems but Oosthuizen rallied to birdie two of his last three holes and draw closer to Choi.
"I didn't putt as well as I have been doing and missed a few right-to-left putts, so I'll be practising those," Oosthuizen told reporters.
His victory at St Andrews and a confident first round in Sweden had been fashioned around accomplished putting.
"All of us misjudged the wind on the 17th and it proved costly for me. After that it was fine, though, and I hit two good shots on 18."
Leader Choi, seeking a second European Tour title to go with seven wins on the U.S. PGA Tour, holed a 25-foot birdie putt and slotted home from 10 feet for his eagle. However, he twice missed putts of around two feet as his form on greens continued to be enigmatic.
He is tinkering with a putting action from outside his right hip, once favoured by Sam Snead, having seen the seven-times major champion using the action in a 1968 magazine.
Choi tried it in last week's British Open but missed the cut and he is loath to use it this week, he said.
"The greens are too sloping here to use that method," he told reporters. "I'm very confident with my swing, though, and I just have to stay patient on the greens."
The 2008 winner of the event, Peter Hanson of Sweden (68) and American invitee Dustin Johnson (73), held third place in the clubhouse on 140, five strokes off the lead.
(Editing by Alison Wildey
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