India have eight wickets in hand and a full day to bat against a fiery South African pace battery.
"The mood in the dressing room is just normal. Our batsmen know what their roles are and who the South African bowlers are. They have studied them and played against them. So we need to dig deep and fight the day out," Penney said.
India lost one more wicket than they would have wanted when Shikhar Dhawan was out caught by Faff du Plessis, with the fielder pulling off a stunning catch at short mid-wicket.
"At this particular stage, he wasn't very happy because the light was poor and they could have come off at any stage. I think he was pretty disappointed," said the coach, describing Dhawan's mood.
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Earlier in the day, Jacques Kallis stroked his way to 45th Test hundred in his last match to put South Africa in a dominating position.
"It is a bit more variable with the old ball. We just wanted to test with reverse swing as well, that was the main reason. It didn't really allow the new batsmen to settle down, as we were relying on reverse swing and thought that was the best strategy," Penney said.