Cape Town - The Proteas need to contain Black Caps skipper Kane Williamson, according to bowling coach Charl Langeveldt.
Williamson steered his side to a comfortable position at the close of play on day two of the first Test against the Proteas - reaching stumps on 177/3.
The Kiwi skipper hit an unbeaten 78 off 146 balls (11 fours) to leave his side trailing by 131 runs with three days still remaining in Dunedin.
Langeveldt says that the Proteas see Williamson as their number one target if they want to seal the Test match.
"I think tomorrow we just have to box smart and then try and contain Kane Williamson," Langeveldt told reporters on Thursday.
"He is definitely the key."
There is doubt over whether batsman Ross Taylor will return for the remainder of the Test match after he retired hurt on 8 with a calf injury.
"I'm not too sure if Ross Taylor will come back, but Ross is obviously a good batsman and they have a few all-rounders coming in," said Langeveldt.
"We still have to bowl well to get them out. Tomorrow morning we have an opportunity and then it's just box smart."
Langeveldt singled out seamer Vernon Philander as the bowler to attack and make the breakthrough for the tourists in the vital morning session.
"Kane is on top at the moment, Vern (Vernon Philander) is a strong character and he'll come back tomorrow morning," said the Proteas bowling coach.
"He'll bowl good areas and he'll be asking questions. But Kane played really well, we can't take it away from him."
Day two also marked the return of Morne Morkel, who bowled for the first time in a Test match in over a year.
Although he went wicketless, Morkel showed plenty of signs of his old self, which was an encouraging sight for Langeveldt.
"Well the best thing was that his pace was up, for the amount of overs that he bowled - I think he bowled really well," said Langeveldt.
"He got it in good areas, but the key thing was that Morne Morkel's pace was back and he was bowling at 100 percent. A plus point for him in that sense."
The Black Caps resume on day three on 177/3 with Williamson (78*) and Jeetan Patel (7*) in the middle (00:00 SA time).