In the movie, R Madhavan essays the role of a boxing coach and national-level kick-boxer Ritika Singh is the leading lady of the movie.
The makers auditioned nearly 100 athletes and zeroed in on Ritika.
"Initially, I was apprehensive about the acting part. I was reluctant (as) I wanted an actor as the film is not about boxing alone, it also has difficult scenes.
But Madhavan and (director) Sudha (Kongara) were adamant that they wanted a real boxer. Madhavan and Sudha wanted a real boxer so that the fights could (be) real," Hirani told reporters here at the promotional event of "Saala Khadoos".
The film directed by Sudha Kongara is all set to release on January 29, 2016.
"I was surprised when I saw her (Ritika's) work," he quipped.
Hirani is known to make films that have a social message, but "Saala Khadoos" is quite different.
"I make feel good films. Sports films are inspiring, they are story of underdogs who come out as a winner. In films there are no fights but people will love this film," he added.
"It is about fighting odds, consequences and staying focused to achieve things," he added.
