The actress was chosen by Anurag Kashyap, who recently premiered the critical success Gangs of Wasseypur at Cannes.
An industry insider told the Hindustan Times: "The logic is simple: in that age group, she is the most talented actor in Bollywood. You don't have an option as good as Anushka.
"Raju Hirani and Aamir Khan choose Anushka for Peekay, so it shows that she is in for big things in the future."
Sharma recently filmed a scene with Shah Rukh Khan at Stansted Airport for a Yash Raj production.
The star made her debut opposite Khan in the hit romantic comedy Rab Ne Bana Di Jodi.
In April, she said that she considered herself lucky to be working alongside the actor again.