Kevin Costner and wife Christine Baumgartner attend the premiere of Draft Day on Monday in Los Angeles, US. Photo: CFP

As the National Football League (NFL) readies for its annual draft of college football players, new film Draft Day pulls back the curtain on the high stakes of the offseason that has helped turn the US' most popular sport into a year-round addiction.

The film, which opens in US and Canadian theaters on Friday ahead of the NFL's three-day draft from May 8-10, stars Kevin Costner and dramatizes the backroom wheeling and dealing of football's general managers as they jockey for the best players and try to fleece one another while trading draft picks.

But in an age of 24-hour sports networks like ESPN and HBO's behind-the-scenes NFL reality show Hard Knocks, Costner said authenticity is crucial to hook a viewer who has seen countless locker-room speeches and front-office interviews.

"If you've ever played the sports you're trying to depict, you don't want people just doing it and messing up completely. People take it really personally," said the 59-year-old Oscar winner, who built his heartland reputation with baseball films Bull Durham and Field of Dreams, and golf comedy Tin Cup.

Costner plays fictional Cleveland Browns team general manager Sonny Weaver Jr, who has to manage upheaval in his personal life and the dueling pressures of which player to draft from the team's owner and its coach.

"For me, I've made a few (sports films), but I always thought they were literate in a sense that the writing was really exceptional, and it was set against the backdrop of each sport, and the big deal there is, 'Can you make those moments be authentic?'" he added.

Draft Day, directed by Ghostbusters filmmaker Ivan Reitman, had the approval and participation of the NFL and several scenes were filmed during last year's draft in New York.

It also features a cameo appearance by commissioner Roger Goodell as well as scripted footage of the fictional draft from NFL Network and ESPN anchors and analysts.

The NFL's annual draft has become big-time viewing for television audiences hungry for football in the offseason. In 2010, the NFL moved the draft to three days from two, with the first round getting its own primetime Thursday slot.