Ashwin, who suffered a side strain during the first ODI in Kanpur, could not participate in the last four games against the visitors. His absence hurt the hosts as they went down 2-3 against the AB de Villiers-led side.
"Ashwin is bowling magnificently. He is absolutely fine," said Shastri.
Ashwin was seen going through his practice drills in full vigour during the team's training session at the PCA stadium here today.
Apart from bowling in tandem with other spinners, the 29-year-old player was also involved in a football game that the cricketers played before moving to the net session.
While Proteas batsman Faf du Plessis had admitted of Ashwin being the main threat for the tourists, opener Dean Elgar also believes that the off-spinner is spearheading the Indian bowling attack for the moment.
Shastri though warned the visitors of concentrating too much on Ashwin and neglecting the other Indian spinners.
"We have got two other spinners, who might just surprise if they focus too much on Ashwin," Shastri said.
