Overnight joint leader Damien McGrane dropped to seven under after three holes of his second round at the Joburg Open before a thunderstorm forced play to be abandoned for the day.
McGrane bogeyed the opening hole before following it with two pars as he fell four shots behind leader Robert Rock.
The 34-year-old from England, chasing a second career win, shot a second-round 67 to hit the front just moments before officials called a halt to play.
Rock, who played the West course, is 11 under par for the tournament after posting an eagle and four birdies on Friday, with his only blemishes being bogies on the eighth and 12th holes.
He signed his card a shot clear of home duo Jbe Kruger and Branden Grace, who both went round the West in 66, adding to their 67s on Thursday.
Another South African, Michiel Bothma, is a shot further back on nine under, as is another in George Coetzee. He could prove to be the best-placed, though, with his second round interrupted after just six holes.
Scotland's Scott Jamieson checked into the clubhouse with a four-under 67 leaving him three shots behind his Anglo rival, while England's Jamie Elson, one of the leaders after the first round, was unable to start his round at all.
Defending champion Charl Schwartzel, four under for the tournament, will have to wait until after all the second rounds have been completed on Saturday morning to see if he has made the cut.