Fisher then bogeyed his last three holes, dropping eight shots in his last four for a 72 when he was on course to better Garcia's opening-round 64.
At one stage Garcia led by five shots as he opened his round with birdies on the first two holes, but four bogeys, including the 18th, spoiled his day and allowed others to close in around him.
"I probably wasn't swinging unbelievably but I kept it under control and kept the ball in play all the time which is hard to do here".
South African Oosthuizen is his nearest challenger as he seeks a first win at a tournament he has long coveted, with Finland's Mikko Korhonen (70) three shots back.
"I have to play really well this week to give myself a chance, even half a chance going into next week, and that's what I'm going to try and do", said McIlroy, who is eighth in the Race to Dubai, nearly two million points behind Molinari. Yesterday the wind felt like it was switching on a lot of holes, and you're looking up in the sky trying to figure it out. "When you can do that here, it's nice to be able to shoot a score like this". "If you do that you give yourself a chance".
South Africa's defending champion Branden Grace is at two under, along with New Zealand's Ryan Fox, while world No.6 Rory McIlroy is a further two shots back.
Justice Ruth Bader Ginsburg released from hospital after serious fall
The next sitting of the Supreme Court isn't until November 26th, so once again, she's not likely to miss a day of work. In response, Trump tweeted that Ginsburg was an embarrassment for making "very dumb political statements about me".
In nine previous appearances at Sun City, 2011 Masters champion Schwartzel has had five top-10 finishes, including being runner-up to German Martin Kaymer in 2012.
"If I can tidy that up tomorrow I should be alright, but obviously I'm pretty disappointed right now", said McIlroy.
"So I feel confident, but transferring that to playing well is a different thing. I kept it under control and guessed some of the winds right, which is always hard here".
"It was good the first few holes today, but I was very scrappy on the way in". I made some good putts here and there.
McIlroy is nearly two million points behind Molinari and needs to win at least one of the remaining two events to overhaul the Italian, who enjoys a lead of just over one million points from Ryder Cup partner and defending champion Tommy Fleetwood.