Off the field Stephen Cook is a man of impeccable manners, effortless understatement and English country house elegance, all of which were useless to him on the field yesterday. What Cook needed was balls - his own and as many as he could soak into his soul in keeping South Africa in the hunt to win a third test that will not be drawn.Happily, Cook proved himself to be not just a pretty face. The kid's got big ones, Jimmy. But you knew that already.Cook's undefeated 81, as butt ugly a solid gold innings as any yet played, was the fist inside the boxing glove South Africa will need to wield with as much care as killer instinct today if they are to become the first side to inflict a 3-0 hiding on Australia at home.story_article_left1"Cookie's just one of those hard-working cricketers, sort of old school," Neil McKenzie, South Africa's batting coach, said."He does it his way and he doesn't always look pretty. But he's got a method that works for him."Mentally he's right up there with some of the toughest guys who are playing cricket at this stage."He's endured a lot of noise about his technique and about how he goes about things, but I'm very happy for him."Cook resumed this morning with South Africa four wickets away from the end of their second innings and 70 runs ahead.They will need many more where those came from to deny their previously tired, timid opponents who have been infused with fighting spirit by the addition to their ranks of three newbloods.McKenzie predicted a tense fourth day: "As you know, South Africans and Australians, we fight to the death."Cook was accompanied this morning by Quinton de Kock, who earned the right of return by surviving three fizzing fireworks from Nathan Lyon to end the day's play.That means the classy Vernon Philander, the ambitious Kagiso Rabada and the outrageous Tabraiz Shamsi are still in the hut. There are runs to be had from that little lot, but the fact that their potential contribution has to be factored in tells us how far South Africa are from emerging from the woods.story_article_right2Would that they could all bat like Cook, whose inner upper lip remained remarkably stiff as he nudged and nurdled some of his runs into the scorebook, squirted others off the edge, and all the while refused to get out with the kind of defiance that had kept Fidel Castro alive for all those years.For two hours another bearded wonder helped Cook remind all which team had dominated the first two tests.But Hashim Amla wasn't in it for the long haul. He fell, as he has done every time he has batted in the series, to the metronomic Josh Hazlewood for 45.JP Duminy, Faf du Plessis and Temba Bavuma were made of less stern stuff.Du Plessis, whom the Sydney Morning Herald has identified as being central to the "ball-sweetening debate", entered to a chorus of boos - like he did in the first innings, when he scored 118 not out."That's pretty bad manners where we come from," McKenzie said of the crowd's behaviour.This time Du Plessis was removed for 12 when he drove Mitchell Starc to gully.Lyon ended Kyle Abbott's shift as nightwatchman after five deliveries, which brought us to Cook and De Kock, the profane and the sacred. It is Sunday, after all.And, as McKenzie said, "We're not on the plane yet."Where we come from, that sounds like a wing and a prayer...