The experienced left-arm spinner would also bolster India's frail batting, which amassed only 376 runs in losing the first Test by an innings and 32 runs.
"We've not completely finalised our playing XI," said captain Rohit Sharma on Tuesday, ahead of Wednesday's first day.
"Everyone is available. There's no injury concerns. We will sit down in the evening and decide what is the right one.
"Having said that, I still feel that we've got a little bit of inexperience in our bowling. Sometimes when you have that, you've got to show some faith in them, show trust in them."
India's batting – and to a certain extent their bowling – failed to come to terms with the lively wicket for the first Test in Centurion, which had pace and bounce.
Cape Town has traditionally been known for movement off the seam, though the Indian captain said at first glance conditions could be the same as in the first Test.
"We know exactly what is required when the conditions are like that," he said. "Based on the pitches, how the conditions are, you have got to respond to that."
That may suggest India will not play two spinners, leaving Jadeja to fight for a spot with Ravichandran Ashwin, who took 1-41 from his 19 overs in the first Test and scored eight runs across two innings.
India have added uncapped seamer Avesh Khan to their squad after he impressed in the white-ball series and for India A against their South African counterparts last month.
