The Springboks capitalised on the numerical advantage, scoring ten points to establish a lead they never relinquished.
It was Ulster 's Ruan Pienaar who ran in the crucial try in that period - while the boot of Pat Lambie was enough to secure victory for the South Africans.
And Heaslip, who has made four RaboDirect PRO12 appearances for the European champions this season, admits he apologised to his Ireland team-mates at the first opportunity after the game.
"I put my hand up straight away when we came in afterwards. I'm a better servant on the field than off it," he said.
"We came out in the second half ahead and as captain I should lead by example, but being yellow carded isn't a good example.
"We were a little bit frustrated we weren't further ahead at half-time.
"They were quite clever about how they played the game when they had the ball.
"But we were still very confident and focused on what we had to do. We knew they'd have a purple patch, but we felt we could keep our momentum."
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