The 29-year-old eight-time victor on the circuit won the Nedbank Golf Challenge at Sun City two months ago, his last appearance on the Tour.
In all, the victor at Sun City last November recorded seven birdies and one bogey and before the turn looked to be slipping out of contention.
English duo Andy Sullivan and Matt Wallace carded three-under 69s to move to five under for the championship while former Ryder Cup victor Jamie Donaldson, who carded the first ace of 2018, is a further two shots back after a one-under 71 which saw the Welshman mix five birdies with four bogeys.
"I got frustrated out there to be quite honest. I think the putting stroke was a little bit quick and I pushed and pulled a few".
"I can get on a little streak like that.when you make one you kind of feel that surge of adrenaline and you run with it". "I drove the ball really well and I felt like I actually played better than yesterday - just didn't really hole the putts".
Adrien Saddier of France fired a course record nine-under-par 63 Friday to share the halfway lead in the South African Open near Johannesburg with Chris Paisley of England. I told myself to stay positive", he said, "I was four or five behind going into the last day at the Nedbank, so I thought if I could get the margin pretty small, I could still have a chance. "I certainly hope that I can keep that trend (of Englishmen winning the SA Open) going". Turning in three under for the round, the local claimed five birdies within six holes during the inward half to leap into contention for first prize.More news: Clemson's Ferrell returning for senior season
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After another birdie at 13, the Frenchman claimed three in a row from 15 to record the lowest score this week in the first European Tour event of the year.
Blaauw said his round would boost his confidence for Sunday's push.
Johnson and Kirk kept clean cards playing on opposite sides of the draw and closed with different brands of birdies on the par-5 18th hole - Kirk two-putted from about 10 feet, while Johnson found a bunker, laid up and hit a wedge to 5 feet.
"Being tied for the lead isn't a position I've been in a lot", Paisley said.
In a field containing five former Major winners, Saddier and Paisley will be thrilled to lead the pack in the second oldest national golf championship after the British Open. "I made a par on two which feels like a bogey and made a bogey on five which was awful, too".
"I'm looking forward to tomorrow big-time". The trio of Denmark's Jeff Winther, Trevor Fisher Jnr and Jacques Kruyswijk are all on 10-under-par.