England's Daniel Brooks claimed a one-shot lead at the halfway stage of the weather-affected BMW SA Open as tournament favourite Branden Grace suffered a late stumble in Johannesburg.
Grace shared the overnight lead with fellow South African Keith Horne after play was suspended on Friday afternoon due to the threat of lightning and edged in front with a birdie on the 14th when play resumed on Saturday.
However, the world number 14 then bogeyed the 17th and 18th to card a 68 and finish seven under par, two behind Brooks after the 28-year-old birdied six of his last 11 holes in a superb 67.
"I didn't get it going this morning and let it slip on the par-five 15th with a three-putt for par and a couple of bad swings to follow that," said Grace, who won twice on the European Tour last season and also compiled a perfect 5-0 record in the Presidents Cup.
At nine under par, Brooks held a one-shot lead over Horne, with Grace and Jbe Kruger on seven under and England's Ross McGowan part of a four-strong group another stroke back.
"It was quite breezy yesterday afternoon and I wasn't playing that great so it was nice to come in for me. It was needed," said world number 508 Brooks, who won the Madeira Islands Open in 2014. "I got out there this morning and played some really nice golf. I started on the eighth and made a good birdie, birdied nine and that got me going.
"It's going to be a long day having played 11 holes this morning but I'll go out there and have some fun. Last year I got off to a really slow start and only started playing well halfway through the year. Hopefully this year it will be the opposite and I'll get off to a good start."
The halfway cut fell at two over par and meant defending champion Andy Sullivan and tournament host Ernie Els both missed out by a single shot, Sullivan having added a 72 to his opening 75 on Friday.
Els resumed his second round on Saturday and gave himself a chance of making the cut with a birdie on the 15th, but could not pick up any further shots and eventually signed for a 74.