Graeme McDowell took a one-shot lead at the Nedbank Golf Challenge in Sun City, South Africa, despite playing an air shot during his second round.
The Northern Irishman's five-under-par 67 contained seven birdies but also a double bogey on the par-five 14th where he hit a rock and missed the ball.
England's Lee Westwood is tied in second place with Martin Kaymer, Robert Karlsson and Jason Dufner on six under.
Simon Dyson is four under while world number one Luke Donald is two under.
"It was a very calm and quiet front nine and an exciting back nine," said McDowell. "I tugged my drive on 14, I was kind of trying to steer it but pulled it into the bush.
"Then I made contact about an inch behind the ball, hit the rock and my club just bounced right over the top. It was interesting because my caddie called it before I hit the shot, he said, 'Be careful your club does not bounce off that rock'."
However, the 32-year-old 2010 US Open champion hit back in style by sinking 20-foot birdie putts at the 16th and 18th.
Masters champion Charl Schwartzel began the day tied for the lead with defending champion Westwood, but struggled to a 74 after running up a double-bogey six on the eighth.
Open champion Darren Clarke, who was last after the first round, moved above Francesco Molinari into 11th place in the select field after he fired a 69 and the Italian slumped to a 77.