Patton Oswalt, left, stars as an obsessed New York Giants supporter in the film Big Fan. (GAT)

Although it's a huge part of our culture, sports fandom is almost never depicted in movies. Sure, there's an endless supply of films about redemption-seeking boxers and gruff football coaches who inspire their underdog squads to victory. But other than a couple of lame comedies (Fever Pitch, Celtic Pride) and an overwrought drama (The Fan), the millions of guys who live and die with their teams – and yes, they are almost exclusively male – have been virtually ignored on the big screen.

'Most filmmakers think that sports fans don't really deserve to be explored in a serious way. They're only treated as fodder for broad comedy. I think they're deserving of at least one serious movie.'

— Robert Siegel, writer-director of Big Fan

"Most filmmakers think that sports fans don't really deserve to be explored in a serious way," says Robert Siegel, writer-director of the new film Big Fan. "They're only treated as fodder for broad comedy. I think they're deserving of at least one serious movie."

Siegel has delivered on that count. Big Fan is a mesmerizing character study of Paul Aufiero (Patton Oswalt), a 35-year old whose support for the New York Giants football team has morphed into an all-consuming obsession. Paul, who lives at home with his mother in Staten Island, works as a parking garage attendant but spends most of his time writing and rehearsing banal rants about the Giants' superiority. When he calls into a local all-sports radio station and occasionally gets to air his views, Paul finds momentary happiness.

This might sound like a set-up for a comedy, but it isn't. Paul's devotion truly knows no bounds, which ultimately leads to serious consequences. By chance, he comes across his favourite Giant, quarterback Quantrell Bishop (Jonathan Hamm), and follows the sports deity into a Manhattan bar, where an encounter with his hero goes horribly awry.

Siegel deftly uncovers the rage and frustration that lies near the surface of modern-day fandom – especially the hateful invective that passes for conversation on U.S. sports talk radio. The writer-director is well acquainted with that world, having grown up on Long Island listening to WFAN, America's first all-sports station. In fact, it doesn't take much prodding to get Siegel to wax nostalgic about the glory days of hockey's New York Islanders in the early 1980s.

Director and screenwriter Robert D. Siegel. (Stephen Lovekin/Getty Images)

"I didn't write this as an outsider or as a sociologist. It wrote it as kind of an outsider and an insider. I'm a big, big sports fan."

Siegel remembers being attracted as a kid to the diverse voices he'd hear on the radio, all of them inordinately passionate about sports.

"It's just interesting to hear people really worked up about the coach's decision to go for it on fourth and long. There's something very compelling about it on a human level. I grew up in middle-class Jewish suburbs and the callers opened this window to another world, which was only maybe 20 miles away, but they were from other parts of the New York area where I had never been: Queen's, Brooklyn, Staten Island. They would all have different accents; it was exotic and exciting. And these are all places I would've been scared to go to in 1980s crime-ridden New York. I guess there was this voyeuristic quality to it."

As his cinematic tastes developed, Siegel gravitated toward Taxi Driver and Midnight Cowboy – 1970s classics about outsiders. "I love those movies about lonely guys walking down dirty New York streets – the kind of person I imagine some of these guys I would listen to [on WFAN] were."

Big Fan owes a stylistic debt to those gritty films. Nothing is sleek or shiny here – virtually all of the locations look grimy, from Paul's poster-laden bedroom to the relentlessly bleak surroundings of his underground workplace. Never has a parking attendant's booth felt this claustrophobic.

The Big Fan screenplay had been bouncing around Hollywood since 2002. After reading it, director Darren Aronofsky asked Siegel to create another script, this one about a down-and-out grappler facing the grim realities of aging. The result was the screenplay for The Wrestler, the buzz picture from last year that launched Siegel's film career.

Clearly, the two stories come from the same imagination. Siegel has tremendous empathy for his characters, and both Big Fan and The Wrestler feel like documentaries about working-class America. Neither film is especially plot-heavy; instead, they each rely on a commanding lead performance. In The Wrestler, it was Mickey Rourke's heartbreaking turn as Randy "The Ram" Robinson; in Big Fan, Oswalt delivers a revelatory study of a petulant man-child who's forced to question his fanatical devotion after seeing his football idol behave in a most unheroic manner.

"Patton is definitely in touch with his angry inner nerd," says Siegel. "He's not a sports fan at all, but he understands nerd obsession and the psychology of caring way too much about something that doesn't really matter in the grand scheme of things. Typically with a role like this, people go for Paul Giamatti, Philip Seymour Hoffman or John C. Reilly. I felt like those guys had done it before, and I wanted to find someone who was a little bit younger. And on a practical level, the film was super-low budget — we didn't even have trailers [for the actors]. This was a great opportunity for Patton, so he was willing to sacrifice and put up with the vagaries of indie filmmaking."

Casting a lead actor who's best known for his stand-up comedy and sitcom work in The King of Queens has lead to unwanted confusion, says Siegel. "When we were [at] Sundance, the catalogue blurb about the movie described it as a hilarious comedy, and it really messed up perceptions of the movie. I really took pains to present it as a drama."

It's not that Siegel lacks comic chops — after all, he was editor-in-chief of the groundbreaking humour site The Onion from 1999 to 2003. Still, he has no interest in creating a massive comedy franchise.

"If you want to make The Hangover, you could earn a lot of money. I just don't really come up with those ideas. I come up with ideas more like A Serious Man. That's the kind of movie I want to make."

Big Fan opens in Toronto and Saskatoon on Nov. 27.

Greig Dymond writes about the arts for CBC News.