Life of Pi, which opens in theaters Wednesday, tells the fantastic (and, of course, fictional) story of a shipwrecked young man forced to journey across the Pacific Ocean in a lifeboat with a Bengal tiger. The movie is earning very strong reviews, but even its most fervent supporters concede that the film is a hard sell. "It's the biggest gamble I've ever taken," says Elizabeth Gilbert, the 20th Century Fox executive who oversaw the film's production. (Watch the trailer for Life of Pi below.) On the eve of Life of Pi's release, there are plenty of reasons to be skeptical about its chances at the box office. Here are five:

1. It cost $120 million to make
Much of the buzz surrounding Life of Pi's troubled production came down to its enormous $120 million budget — an expense that almost got the film canceled before filming could begin in 2010. (Director Ang Lee finally convinced executives to trust his vision for the film.) Much of the budget went to computer-generating the film's animals, which include a zebra, an orangutan, a hyena, and a tiger. The production crew also built a 1.7-million-gallon water tank in Taiwan to replicate Pacific storms in a controlled environment.

2. It's extremely difficult to market
Unlike most of Hollywood's biggest contemporary releases, Life of Pi isn't a sequel and isn't based on a comic book, video game, or other franchise property. Though Yann Martel's 2001 novel sold 9 million copies worldwide and won the Man Booker Prize for fiction, its unusual, surreal narrative is difficult to explain to the uninitiated in a 2-minute film trailer — and all but impossible to break down in a 30-second commercial spot.

3. Its story is overtly spiritual
Life of Pi begins with the promise that Pi's story will reveal the existence of God — an unusual conceit for a Hollywood blockbuster, which only becomes more complicated when the young Pi embraces Hinduism, Christianity, and Islam simultaneously. By setting such a lofty philosophical and spiritual goal, Life of Pi threatens to alienate a large portion of its audience and makes a promise difficult for even the greatest of films to fulfill.

4. It has no movie stars in its cast
Hollywood wisdom holds that it takes a famous name on a marquee to sell most films — particularly a film as idiosyncratic as Life of Pi. But Life of Pi stars Suraj Sharma, a 17-year-old first-time actor, who anchors an international cast of unknowns. At one point in its production, the cast included Spider-Man's Tobey Maguire, who was set to play the writer interviewing the film's protagonist, but Ang Lee opted to recast the role after deciding that Maguire was "too jarringly recognizable."

5. It faces fierce competition from other movies
This week's new releases include Silver Linings Playbook, a crowd-pleasing romantic comedy and early Oscar favorite; Hitchcock, a drama aimed squarely at adults; and Rise of the Guardians, an animated movie sure to draw families. Each of those new films takes a bite out of Life of Pi's potential audience, and with upcoming competition from films like The Hobbit: An Unexpected Journey and Les Miserables, competition will only get fiercer.

Sources: Box-Office MojoThe Los Angeles Times (2) (3), New York Daily News, Total Film