George Coetzee recorded a stunning 65 on day two at Whistling Straits to move into contention at the US PGA Championship.
The South African, who has two European Tour wins so far this season at the Tshwane Open and AfrAsia Bank Mauritius Open, opened with a 74 but went nine shots better second time round to sit two shots behind leader David Lingmerth who was seven under after 14 holes of his round.
He opened with two birdies and recorded two in a row again at the fifth and sixth before blotting his copy book with a bogey on the ninth.
That did not halt his momentum, however, and he picked up two further shots on the 10th and 11th before putting his second shot on the par five 16th to five feet and claiming an eagle.
A seventh birdie of the day followed on the 17th but after he found the sand and had to chip out on the last, he finished with a bogey.
Lingmerth had first held the lead after five holes as he started with three early birdies but went double bogey-bogey-bogey from the seventh to the ninth to slip back.
His erratic round continued with a birdie on the tenth, bogey on the 11th and then three birdies from the 12th to 14th to leave him seven under.
Dustin Johnson had set the first round target on six under and he was amongst the later starters.
Henrik Stenson made the turn in 31 as he surged up the leaderboard to sit just three shots off the lead
The 2013 Race to Dubai winner had endured a frustrating first round as he recorded a double, three bogeys and a single birdie in a 76 which looked like it could endanger his chances of making the cut.
But the Swede, starting on the tenth, birdied his opening hole and the 11th and was soon back to level par as he picked up further shots on the 15th and 16th.
He made it three birdies in a row on the 17th and picked up further shots on the second, fifth and sixth to sit four under after 15.
Jordan Spieth was alongside Coetzee on five under as he appeared to be winning the battle with playing partner and defending champion Rory McIlroy.
The World Number One missed from 18 feet for birdie on the tenth and was unable to get up and down for birdie on the par-five 11th after a badly pulled approach.
World Number Two Spieth had birdied the 11th but failed to get up and down from a greenside bunker on the 12th to drop back alongside McIlroy.
After making his sixth par in succession on the 15th, the four-time Major winner finally carded his first birdie on the par five 16th by two-putting from 30 feet.
Spieth then got up and down from the back of the 16th green to keep pace and the duo were two under after eight holes.
One of McIlroy's three bogeys on Thursday came on the 18th and worse was to come on Friday, the 26 year old mis-hitting two chips from left of the green to run up a double bogey six and drop back to level par.
Looking to become just the third player after Ben Hogan and Tiger Woods to win three majors in a season, Spieth chipped in on the 18th and then holed from 12 feet for birdie on the first.
McIlroy was desperate to make amends for the double bogey and charged his birdie attempt on the same hole four feet past the hole, but produced the ideal response on the par five second, chipping in for an eagle to get back to two under.
Spieth made another birdie on the par three third after putting his tee shot to within five feet to get to five under.
