Priyanka will essay the life story of Olympic medal-winning boxer Mary Kom in the film, produced by Sanjay Leela Bhansali.
Last year, biopic on life of national sprinter Milkha Singh, played by actor Farhan Akhtar, had won the film several accolades, while Irrfan's stint as Paan Singh Tomar in the 2012 film of same name bagged two National awards.
The 'Fashion' star made it clear that it was wrong to compare the film with 'Bhaag Milkha Bhaag'.
"I think you can't compare Mary Kom with Bhaag Milkha Bhaag. For the first time a film has been made on life of a female athlete. It is disrespectful to say it is a trend of sports biopic film. Mary Kom is the pride of our nation," Priyanka told reporters here at the trailer launch of the film today.
The 32-year-old actress said 'Mary Kom' is so far the toughest film of her career.
"It is the most hardest film of my career. To bring her (Mary Kom's) personality on screen was the hardest part. To bring the part of a fighter, a homemaker, and a mother was a challenge," Priyanka said.
Priyanka said she was deeply touched with the real life journey of the pugilist.
"She comes from a small town farmer's family. Sports, in itself is a difficult thing in India, but she did it," the actress said.
To get into the skin of the character, Priyanka underwent rigorous training and has even spent 15 hours training to have the muscular look.
Drawing parallels with real life instance of Kom, where her father tried to stop her from being a boxer, Priyanka said she too had her share of struggle.
Directed by debutante Omung Kumar, 'Mary Kom' is slated to hit theatres on September 5.