Schwartzel smashed the event's 54-hole scoring record in the process, ending the day at 21-under 195 -- good for a formidable lead over Gregory Bourdy at Leopard Creek Country Club.
The South African came into the day tied for the top spot with Bourdy but began a hot streak with three straight birdies from the fifth hole and never looked back.
Bourdy stumbled to a 2-over 74 Saturday, giving him sole possession of second place at minus-11.
Sharing third at 10-under 206 were Branden Grace and Kristoffer Broberg (both 5-under 67s) and Steve Webster (70).
Holding sixth place at minus-9 was Keith Horne (68).