Zaheer Khan has been ruled out of India's Test series in Sri Lanka because of a shoudler injury.
The left-arm paceman, 31, has been told to rest the problem by team doctors and will miss the three Tests.
"Zaheer Khan has been ruled out of the forthcoming Sri Lanka series because of a shoulder injury," Board of Control for Cricket in India secretary N Srinivasan confirmed.
"The All-India Senior Selection Committee has chosen Abhimanyu Mithun to replace him."
Seam bowler Mithun, 20, is uncapped at Test level and has played just 10 first-class matches.
He made his one-day international debut against South Africa in February, taking 0-63 from eight overs.
The series opener takes place in Galle from July 18-22, in what will be Sri Lanka spinner Muttiah Muralitharan's final appearance for the hosts before his retirement from the five-day format.
The second and third Tests are both in Colombo, at the SSC (Jul 26-30) and P.Sara Oval (Aug 3-7).