Graeme Storm saw his lead cut to one shot in the final round of the BMW SA Open hosted by City of Ekurhuleni as Rory McIlroy turned in 33 at Glendower Golf Club.
Storm came into Sunday with a three-shot advantage but World Number Two McIlroy made a birdie-birdie start and then added another on the eighth, while Storm made a single gain on the third to get to 18 under.
The Englishman has been resilient all week and he made a host of par saves to keep McIlroy at bay but the 27 year old is nine under par for the back nine this week.
England's Jordan L Smith was then at 16 under alongside local favourite Trevor Fisher Jnr.
McIlroy had looked to be in some discomfort with his back problem on the range but he did not show it on the first tee as he took out the driver and, while he found the rough, he put his approach to five feet and opened with a birdie.
Storm holed a nervy seven-footer for par but Smith three-putted for bogey to drop five back.
McIlroy had spoken about the importance of a fast start and he got one, rolling his eagle effort right up to the side of the cup on the par five second for a tap-in birdie but Smith went one better, making his eagle from 15 feet to get to 14 under.
Storm needed three putts to make his par and his lead was swiftly cut to one shot.
Smith continued his excellent recovery with a beautiful tee-shot to birdie the par three third and Storm followed him in to edge back two ahead.
McIlroy just looked to have lost some of that early momentum but there was no stopping Smith, who rolled in a massive birdie putt on the fourth to join the four-time Major Championship winner in second.
Storm made a smart par save from a bunker on the fifth with McIlroy doing the same on the sixth but it was Smith on the move, the 24 year old rolling a 25-footer up and over the ridge on the sixth green for another birdie.
All that momentum was halted on the seventh, however, as Smith put his second over the back of the green and then, from a poor lie, sent his third over the green and into a bunker en route to a double-bogey.
Smith made it four birdies out of four on the eighth with McIlroy getting to five under for the week on that hole with a gain of his own, and when Storm only made a par the lead was back to one.
Storm then hit a ragged tee-shot on the ninth but saved par again to keep his nose in front and take his bogey-free run to 50 holes.
Fisher had fallen back with a 71 on Saturday as all those around him picked up shots but he was five under for the day through 12 holes with an eagle, five birdies and two bogeys.
Dean Burmester was then at 15 under, two shots clear of Thomas Aiken, Edoardo Molinari and Richard S Johnson.
