One of the finds of the India's U-19 World Cup triumph, Nagarkoti sustained the injury before the tournament but the announcement came only today as KKR lost a second pacer this season after Australian spearhead Mitchell Starc.
The 22-year-old Prasidh has played 23 matches so far since 2015, three in the T20 format but his record in the 50-overs format has been impressive.
Prasidh has 33 wickets in 19 matches at an average of 21.27 and an economy rate of 4.74, with a best show of 3/37 in Karanataka's Vijay Hazare Trophy against Saurashtra in February.
"Pleased to welcome Nayar to the KKR support staff. The younger talent of the team will particularly benefit from Nayar's experience and mentoring," KKR CEO Venky Mysore tweeted, without specifying Nayar's role.