"MS Dhoni: The Untold Story", due for release on September 30, charts the rise of India's limited-overs captain from boy to train ticket collector to World Cup glory.
Actor Sushant Singh Rajput, who plays Dhoni, told AFP in a video interview that filming scenes that dealt with the death of the cricketer's former girlfriend had been heart-rending.
"It was very difficult because, after we did the preparation, in my head I was him and everything that was happening was actually affecting me," said the 30-year-old.
In 2002 Dhoni was in his early 20s and trying to break into India's national team when his girlfriend, Priyanka Jha, was killed in a road accident, according to Indian media reports.
A music video released by producers as a teaser shows Dhoni's character romancing his sweetheart, played in the movie by Disha Patani, just before her death.
Rajput said that it was a particularly moving scene to film. "It was just before I lose her... I was emotional," explained Rajput.
The film, directed by Neeraj Pandey, includes scenes from Dhoni's childhood when football was his passion as well as his years as a young ticket collector. It culminates with his heroics at the 2011 final.
Rajput, who describes himself as an "ardent" cricket fan, said his preparations for playing an icon had been "exhaustive".
"People already know the way he talks, walks, plays his cricket so I realised very early that it was a possibility that I could act well in the film but at the same time not be very convincing," said Rajput.
The Hindi actor watched "hours and hours" of videos of Dhoni and met the star several times to study his mannerisms.
"There was a certain level of subconscious imitation and it happened from completely immersing myself in him, either thinking about him or looking at him or behaving like him," said Rajput.
Dhoni told a promotional event in New York that he hadn't enjoyed relaying elements of his life.
"What was most difficult for me was to narrate the story and all of that because I am somebody who lives in the present," he said, according to footage broadcast by NDTV news.
Rajput says he has left no stone unturned in ensuring the cricket scenes would be convincing, even mastering Dhoni's trademark "helicopter shot".
"We would carefully analyse it and fix the bowling machine into one spot and then we would play the same shot at least 200, 300 times a day for a week to a point that it came naturally," he said.
The 35-year-old Dhoni, nicknamed "Captain Cool", is idolised for leading India to victory over Sri Lanka in the 2011 World Cup final. The skipper hit an unbeaten 91 off 79 balls, including a match-winning six.
Rajput said the memory of Dhoni's exploits at Mumbai's Wankhede Stadium gave him "goosebumps".
But what did the famously taciturn Dhoni think of the film's final cut?
"He was very moved by it but he didn't say anything. He kept quiet for 15 minutes, smiled and then left," said Rajput.
Source : https://sports.ndtv.com/cricket/mahendra-singh-dhonis-biopic-shows-india-captains-tragic-heartbreak-1467381