Ekurhuleni, South Africa, Nov 17, 2012 (AFP) - At 13 under par, 26-year-old Coetzee is tied in second place with Sweden's Magnus A Carlsson, just three strokes behind leader Henrik Stenson, who had his worst round yet at 69 after 66 and 65 in the previous two rounds.
His round puts him only one stroke behind the lowest score in SA Open history, after John Bland who shot a 62 at the Durban Country Club in 1993.
"It's great to shoot a 63 and I'm very happy, but I have to forget about it as soon as possible," said the Pretoria native.
"I've got to go out tomorrow. If the wind pumps and they put the flags in ridiculous places then 63 is definitely not an option."
The players teed off later since the second round had to be completed after thunderstorms interrupted play on Friday.
Trailing Sweden's Stenson by nine strokes after round two, Coetzee started the third with two birdies and then an eagle on the par-four fourth hole. After bogeying the 12th and 15th holes, he ended strongly with birdies on the 17th and 18th.
"I felt I handled my bogeys a lot better than in the past. Before I would put pressure on myself to make birdie the next hole, but I just waited for my opportunities," he said.
Despite a disappointing show, former world number four Stenson's experience however shone in a consistent lead -- first with three strokes, then one, then four and finally three.
"Things were going well and then I bogeyed ten and missed a birdie chance on 11, so I really felt like I left two out there," he said.
"Overall I'm happy. I'm still in the same position, even though I've got George (Coetzee) breathing down my neck."
He was cautiously optimistic about the final round, where a high finish will ensure his place in the Race to Dubai next week.
"Three shots is enough if you're playing the last, but it's not going to be decided until late here. George was on fire today, but sometimes it's hard to follow up a low round with another low round."
South African Darren Fichardt ended the round six strokes behind Stenson with ten-under-par 206, and one ahead of his countryman, first-round leader Merrick Bremner.
Former world number one Martin Kaymer meanwhile lagged behind with eight strokes with eight-under-par 208 after round three. The German almost arrived late for the start because he worked out in the gym.
"I was doing weights and my feel was gone a little bit for the first three holes, so I made a few too many putts. I played really nice and made a lot of good shots and had plenty of chances, but I missed too many putts to catch Henrik," he said.
Masters 2011 Champion Charl Schwarzel slid further behind, with double-bogeys on the fourth and sixth holes, and consecutive bogeys on the 17th and 18th that saw him finish with 74 strokes, well behind his 68 in the first two rounds.
Scores after the third round of the SA Open over the par-72, 7096-metre Serengeti Golf and Wildlife Estate on Saturday:
200 - Henrik Stenson (SWE) 66-65-69
203 - George Coetzee (RSA) 70-70-63, Magnus A Carlsson (SWE) 68-67-68
206 - Darren Fichardt (RSA) 68-70-68
207 - Merrick Bremner (RSA) 64-70-73
208 - Martin Kaymer (GER) 70-70-68, Thomas Aiken (RSA) 73-66-69, Matthew Carvell (RSA) 66-72-70, Allan Versfeld (RSA) 69-69-70, Michael Jonzon (SWE) 68-69-71
209 - Shaun Norris (RSA) 72-70-67, Michiel Bothma (RSA) 69-69-71
210 - Trevor Fisher Jnr (RSA) 69-70-71, Tommy Fleetwood (ENG) 70-69-71, Jake Roos (RSA) 68-71-71, Marc Warren (SCO) 70-69-71, Jaco Van Zyl (RSA) 70-72-68, Peter Whiteford (SCO) 69-69-72, Charl Schwartzel (RSA) 68-68-74
211 - Ryan Cairns (ZIM) 69-71-71, Martin Wiegele (AUT) 72-69-70, James Kingston 71-68-72, Knut Borsheim (NOR) 73-69-69, James Kamte (RSA) 69-74-68, Oliver Bekker (RSA) 68-69-74, Lloyd Saltman (SCO) 70-66-75
212 - Andrew Johnston (ENG) 71-70-71, Espen Kofstad (NOR) 69-70-73, Markus Brier (AUT) 71-71-70
213 - Peter Gustafsson (SWE) 71-70-72, Jorge Campillo (ESP) 70-71-72, Matthew Southgate (ENG) 70-71-72, David Hewan (RSA) 71-70-72, Garth Mulroy (NIr) 75-67-71, Chris Swanepoel (RSA) 73-69-71, Adrien Bernadet (FRA) 68-71-74, Michael Hollick (RSA) 72-71-70