Donald was two shots clear of overnight leader Ross Fisher on 10-under-par and his round was blemish-free and a brilliant display of precision golf.
Fisher was also two shots ahead of his nearest challengers after a battling two-under-par 70, with Frenchman Alexander Levy on six-under and Danny Willett on five-under-par after a 68.
Donald announced himself as ready to return to the top of world golf as the former world number one produced a dazzling round with nine birdies, six of them on the front nine which he has usually found harder to deal with on his seventh visit to the Gary Player Country Club.
“Obviously nine birdies around this place is a great round and something I was very pleased with. It’s been a while since I played such a solid round. I gave myself a lot of good opportunities today, I didn’t put myself into too much trouble. Obviously when the putter is warm, it’s always one of my best weapons in the bag, so it was nice to roll in a few today,” Donald said.
The 36-year-old – he turns 37 on Sunday – described himself as always feeling in control during his round and that was certainly not the impression Fisher, Marcel Siem or George Coetzee gave as the final three-ball were overtaken by the first man to win both the European and PGA tour moneylists in the same year.
The trio all made silly mistakes as the notorious Sun City rough punished their waywardness.
While Fisher held it together well enough to stay in touch with his fellow Englishman Donald, Siem was left six shots off the pace after a 72 and Coetzee was eight strokes back after a disappointing 74.
“It was a strange day, the total opposite from yesterday. It started really nicely, but all of us had problems on the golf course today. It was not like yesterday where we fed from each other. I felt like we were never going to finish, and on 16, we felt the whole tournament was over already. We played five hours, two minutes, just had a really long round and we didn’t play as well as we did yesterday. Unfortunately the few chances we had on the back nine didn’t drop,” Siem lamented.
“It’s a tough golf course and I don’t feel like I played probably as solid as yesterday. I didn’t hit it as good off the tee. But I still felt like I played pretty solid. I hit one poor tee shot on 14 which cost me a six and had to take a penalty drop there. I got it to five‑under after 11, so I was hoping to kick on and reproduce 66 from yesterday or even a little bit better. But unfortunately it wasn’t meant to be, so I still shot under par, even with a couple of those loose shots coming in.
“Today it just seemed like every putt we over‑borrowed. I hit at least half-a-dozen, if not seven or eight putts, that I hit exactly where I wanted to hit it, and just unfortunately was over-reading the greens today,” Fisher said.
It was left to Frenchman Alexander Levy to act as the challenger to the English dominance as he posted a solid 70.
“It was a good 70, I’m happy because it’s not my best golf but I managed the golf course well. It’s always good to play 70 on this golf course, it’s very difficult and it’s hot,” Levy said.