Set to chase a daunting 381 to win, Pakistan were 153 for 3 at the close, needing another 228 runs. They have Asad Shafiq looking good on 47 and with him is Babar Azam on 17.
"It's going to be quite tough," said De Kock. "The pitch has flattened out. It's definitely got better, surprisingly. I thought with the new ball it would do a lot more than it did."
Realistically, though, the odds favour the home team with only captain Sarfraz Ahmed, a couple of all-rounders and the tail to come.
"We'll have a chat about it tonight. They have a couple of decent batsmen in the mix so we'll have to box cleverly tomorrow," said De Kock.
Pakistan bowling coach Azhar Mahmood said the remaining Pakistan batsmen would need to follow the example of De Kock and Hashim Amla, who enabled South Africa to recover from a precarious 93 for 5.
While Amla patiently compiled 71 off 144 balls, the left-handed De Kock played fluently as the pair put on 102 for the sixth wicket. De Kock also shared an eighth-wicket stand of 79 with Kagiso Rabada.
"Our plan was to get them out so we would be chasing 270-280 but credit goes to De Kock and Amla," said Mahmood, who said he remained confident.
"We've done this before. Babar and Asad are batting really well. If they bat for a long period of time, we've got a really good chance. Like I said in the morning, when you get 50, you have to turn it into 70, and then on to 100.
Mahmood said at least one of the remaining batsmen would have to get a century.
"If these guys do the same thing that Amla and De Kock did we've got a chance," he said.
Mahmood agreed with De Kock that the pitch was playing easier but he cautioned that there was some uneven bounce towards the close on Sunday.
"I think the pitch flattened out a bit. For the last three days, all sides opted for the heavy roller and the pitch flattened out. I think our plan was to get them out for less than 50 or 60 runs today, so we'd have to chase 270 or 280. But credit goes to de Kock and Amla.
"They played really well. They left the ball well, and when they got opportunities, they hit boundaries. On this ground, there are a lot of boundary options. You don't get lot of runs by singles, because boundaries can be had on both sides."
First Published: January 14, 2019, 9:50 AM IST