While Rajat was to initially essay Rishi Kapoor's younger brother in the film, Manoj was to play a tough police officer.
Sinha said in a statement: "I always wanted Manoj Pahwa and Rajat Kapoor in the primary cast for 'Mulk'. While I had envisaged a different role for both of them in the film, it was only when they came in together on sets after the recce did I realize that they were both meant to play different roles.
"They were both pretty quick in adapting to a new role."
The film is based on a series of true events and is slated to hit the screens on August 3.
Rishi is happy about working with Rajat.
"Though we have worked in just two films, a lovely co-actor and poker player, Rajat Kapoor. The only irritant about him is he is a teetotaller, unlike me, and doesn't carry a mobile. An under-used actor waiting to burst. Go man go," Rishi tweeted on Saturday.
Presented by Kamal Mukut and Soham Rockstar Entertainment, a Benaras Media Works production, the film is produced by Sinha and Deepak Mukut. The film also features Prateik Babbar, Ashutosh Rana, and Neena Gupta.
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