The home side lost the match by a massive 214 runs in Mumbai last night, giving South Africa their first bilateral series win on Indian soil.
The Indians crumbled while chasing a mammoth target of 439 after the visiting team rode on swashbuckling hundreds by opener Quinton de Kock, Faf du Plessis and captain A B de Villiers.
The home bowlers cut a sorry figure in the face of the Proteas assault and all of them conceded over 6 runs an over.
In fact, Gavaskar said bowling is a massive cause of concern for the Indian team as was exposed by the South African onslaught at the Wankhede.
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"Bowling is a major worry for India now. We have seen in the T20I and ODI series how they have been ordinary. The Wankhede pitch had turn and good carry. But the Indian bowlers did not bowl accordingly. The fast bowlers were constantly using short pitched deliveries but at 135 kmph," he explained.
The Indian attack was without its regular spin spearhead R Ashwin, who is nursing a side strain, and Gavaskar felt the offie should not be rushed back.
"I also think India missed Ashwin badly. I know he is too eager to play. He missed the last few matches but I saw him bowling in the nets ahead of the third ODI. I think he should not rush things as a side strain can stay with you for long. He should be patient to recover before the Test series," said Gavaskar.
"He is a superman. He is incredible. I think the secret of his success is his positioning. He can read the bowlers' mind and can get into the hitting position quite well. India need to find a solution to tackle him ahead of the Test series," he said.
"Also I also think Kagiso Rabada has been the find of this series. He is always eager to learn and is very down to earth. Rabada has good pace also and he will go a long way," he added.