JOHANNESBURG: Indian seamer Shardul Thakur pursued a simple formula for success as he took seven wickets on the second day of the second test against South Africa at the Wanderers on Tuesday.

India's fourth choice bowler destroyed the home team's top order as he took five wickets before tea and then finished with figures of 7-61 in 17.5 overs for the best bowling performance by an Indian in a test in South Africa.

"There was some help in the pitch, so all you had to do was keep coming hard at the batsman, bowl in the right spots," he explained to a virtual news conference after the close of play.

"The ball was kicking in and it was staying low a bit, so all I did was to try to hit my lengths."

"It was my best figures, but I always say the best is yet to come," he added.

Thakur's performance took much of the pressure off the rest of the Indian bowling attack, with Mohammed Siraj struggling after suffering a hamstring strain on the first day on Monday.

It was only the sixth test for the 30-year-old, who had played back-up to the formidable attack of Jasprit Bumrah, Mohammed Shami and Siraj but burst out of their shadow on Tuesday.

"In overseas conditions, all four seamers have an important role to play and it's good that we were able to do it in a partnership."

India bowled out South Africa for 229, allowing the home side a slender 27-run lead after the first innings. The tourists were 85-2 at close on Tuesday, 58 runs ahead with three days left to play.