De Kock played a well-paced knock of 103 off 118 balls to help the visiting side notch a challenging score of 270-7. In reply, India could only manage 252-6 in the face of some tight bowling that saw the run-rate spiral from the mid overs.Opener Rohit Sharma rattled up 65 but Virat Kohli (77) and captain Mahendra Singh Dhoni (47) could not step up the run-rate. Both of them fell to Morkel, who finished with 4-39.
Rohit, who scored 150 in the opening ODI at Kanpur, struck two sixes and seven fours during his 74-ball innings but was foxed by a shorter delivery from Duminy who happily took a return catch.
The boundaries dried up between the 30th and 40th overs with Kagiso Rabada, Morkel and Imran Tahir coming up with some tight overs. There was a period of almost 10 overs without a boundary - between 30.1 and 39.5 overs — and it was always an uphill task with 86 needed in the last 10.
"I thought 270 was a par score but the wicket kept getting lower and slower and the dew didn't help us out," Dhoni said. "It became a bit two-paced and it was difficult to play the big shots."
Earlier, de Kock once again flourished against the India attack as he struck one six and 11 fours en route to his fourth century in seven innings against India and seventh ODI ton overall.
The left-hander was involved in a 118-run third-wicket stand with Faf Du Plessis (60) as South Africa put up a determined display after choosing to bat.
De Kock struck some crisp drives down the ground and showed enough footwork to counter the spinners.
"It was a very special batting performance," South Africa captain A.B. de Villiers said. "Quinton answered a lot of questions. We were looking at 250 as a par. The way we fought back with the ball was special."
De Kock was cramped for space by the bowlers early on but prospered during a 72-run opening stand with fellow left-hander David Miller (33).
De Kock reached his century with a four off seam bowler Mohit Sharma but was run out soon after by a throw from Shikhar Dhawan at mid-wicket during a phase in which South Africa lost three wickets in nine deliveries with du Plessis and AB de Villiers also dismissed.
South Africa slipped from 205-2 to 210-5 by the 41st over and appeared to lose out on a chance to swell the total further.
Du Plessis fell to Mohit after scoring a third consecutive fifty of the series, albeit a lucky one. Suresh Raina and Shikhar Dhawan failed to latch on to chances while Du Plessis was caught by Virat Kohli at long-on off Mohit when on 16 but replays showed it was a no-ball.
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