Sehwag strained a ligament in his left ankle during South Africa's innings last night and according to the Indian team's media manager Dr R N Baba, the right-hander has been advised rest for 14 days.
Sehwag, who had a poor World Twenty20 in Sri Lanka, scoring only 54 runs in three innings at a strike rate of 112, suffered the injury while celebrating Jacques Kallis' dismissal off Irfan Pathan in the fourth over.
He limped off the field to be replaced by Manoj Tiwary, and did not return to the field again.
The injury comes as a big blow for Delhi Daredevils of whom Sehwag remains a key player despite relinquishing captaincy duties for CLT20 to be held in South Africa from October 9.
The Daredevils are scheduled to open their campaign against Kolkata Knight Riders on October 13 in Centurion.