Paterson, 30, has previously played limited overs internationals for South Africa and captain Faf Du Plessis hinted he could be in line for a test debut, though he stressed no decision had been made yet.
"We are considering the possibility of looking at someone like Dane Paterson," Du Plessis told reporters. "But we have not decided that yet. Obviously for who would be the big question we need to answer. That we will decide this afternoon, if he does come in.
"It’s about the nature of the ground, conditions here and style of bowling that can work at St George’s. But if you do that (play Paterson) you are going in with one less batter or no spinner.
"And there is merit for having both. You need a spinner at St George’s and you also need a long batting line-up, so it is not an easy decision. It is something that we are talking about as an option on the table."
The wicket in Port Elizabeth has produced reverse-swing in recent tests, and Paterson would be a player who can help South Africa extract that advantage out of the pitch.
"Reverse swing generally plays a role here, you need a wind, dry hot air blowing to get the ball dry. If there is something that can scuff up the ball then that might speed it up," Du Plessis added.
"What do we need to get 20 wickets? If we feel what we have is enough (in the current bowling line-up), then that settles the argument.
"It is something that myself, (coach) Mark Boucher and (batting consultant) Jacques Kallis have spoken a lot about and we will make a decision based on what we see on the pitch."
Du Plessis also acknowledged that some expected rain around the middle of the test could lessen the impact of reverse-swing on the game.
"I have heard that there is some rain maybe on days three and four, if you have that then it fights against reverse-swing. So our decision will also be weather dependent," he said.
The South African is expecting another hard-fought test after they claimed the first match in the four-game series by 107 runs, only for England to bounce back with a 189-run victory in the second.
"Both teams are similar. There are one or two guys not scoring as many runs as they would like to. We are very evenly matched at the moment," he added. (Editing by Christian Radnedge)