Ever since Robert Downey, Jr. strapped on the Iron Man armor back in 2008, the Marvel Cinematic Universe has been nothing short of a financial juggernaut. One success after another, year after year, leading up to Marvel studios' crown jewel: the record-shattering success of Marvel Studios' "The Avengers" in the summer of 2012.

As 2013 began, many critics warned of "superhero fatigue," and their predictions of doom, gloom and bursting bubbles persisted... until "Iron Man 3" raked in over a billion dollars worldwide that May. It was followed by "Thor: The Dark World" in November, another film whose box office numbers were pretty stellar on their own.

2014, however, is a new year, and with every new summer blockbuster season comes a series of fresh challenges. Not satisfied to rest on its laurels (Well, there will be some laurel-resting going on; "Captain America: The Winter Soldier" opens in April) Marvel is branching out with Phase 2 of their Cinematic Universe roll-out, which includes new -- and lesser-known -- commodities.

WATCH: Marvel's First "Guardians of the Galaxy" Trailer

Enter the "Guardians of the Galaxy": Easily the least popular superhero squad to appear on-screen for Marvel thus far, and the strangest, most fantastical concept it's ever tried to thrust into the mainstream.

And, by a wide margin, the biggest risk the Disney-led Marvel film franchise has ever taken. With risk comes the possibility of reward, but also the chance of derailing its juggernaut -- if only for a single film.

Don't get me wrong, true believers: I'm going to be at "Guardians of the Galaxy" opening night, popcorn in-hand, preparing to cheer like the spastic fangirl that I am at the first sight of a CGI raccoon or a talking tree. And yet, despite an overwhelmingly positive reaction to the film's first trailer online, some of the more casual movie-goers who make up Marvel's film audience may not share in my unbridled enthusiasm.

And that's the primary issue I see with this film: the lack of mainstream appeal. You could make the argument that some previous Marvel films were risky, with lesser-known heroes in the titular roles. Tony Stark certainly wasn't a household name prior to 2008's "Iron Man," and that risk more than paid off. Audiences weren't exactly clamoring for a Captain America movie set in the 1940s, but that worked out just fine. "Thor" -- possibly the biggest roll-of-the-dice thus far -- turned out to be a huge success, despite taking place in an otherworldly sci fi-draped-in-fantasy setting (a genre that doesn't always translate well to the Muggles.) Even though the aforementioned characters lacked instantly-recognizable names, they all existed in the collective consciousness to some degree. The mere mention of "Guardians of the Galaxy," on the other hand, leaves the majority of people scratching their heads; the modern comic book incarnation of the Guardians has only existed since 2008, and despite the recent Marvel NOW! "reboot" with writer Brian Michael Bendis at the helm, they don't exactly possess the rich history of their cinematic counterparts.

Upon closer inspection, "Guardians of the Galaxy" lacks a number of other key ingredients Marvel's recent films had going for them. A glaring omission is star power. "Thor," "Captain America" and "Iron Man" had a number of well-known, critically acclaimed faces adorning their one-sheets; Gwenyth Paltrow, Jeff Bridges, Tommy Lee Jones, Anthony Hopkins, Natalie Portman -- the list goes on. On the flip side, "Guardians'" cast isn't exactly overflowing with proven box-office draws; featuring pro wrestler Dave Batista to TV's "Parks & Recreation's" funny man Chris Pratt, many will be scouring IMDb in order to find a familiar face in this group. The film's biggest star is arguably Zoe Saldana, whose most notable work was as Neytiri in 2009's "Avatar," where she played a CGI-enhanced blue alien -- which makes her perfect for the role of a makeup-enhanced green alien.

"Guardians" director James Gunn, is another question mark. Before helming his first big-budget blockbuster for a major studio -- one that will be compared to the other Marvel Studios films it is intrinsically linked too -- Gunn directed indie genre films like "Slither" and "Super" that were deliberately left of center. Prior to "Guardians," the scope and scale of his films weren't intended to appeal to as broad an audience as Marvel is aiming for. As both writer and director, Gunn is nothing if not an unconventional choice; whether that will pay off for Marvel remains to be seen, and is something we can't gauge based purely on the first trailer.

POLL: How Would You Grade the First "Guardians of the Galaxy" Trailer?

Another stumbling block could be the concept. While "Man of Steel" and Thor have each featured grounded, real world elements, the former was sci-fi lite, while the latter was a fantasy-fueled adventure that spent most of the first film stripping away the fantastic and finding the man at its center. "Man of Steel's" Krypton, despite a couple dragons and a bellowing Bantha in the opening scene, featured an all-human cast, while Thor's Asgard looks like somthing Rome would have evolved into after a few thousand years. "Guardians" is going to take things measurably further than both, and delve into a level of science-fiction that dates back to the original "Star Wars" -- body paint, aliens, and settings that are going to be much less recognizable than those found on Earth, as well as those in the aforementioned films. Are viewers ready to accept a superhero film where the five main players include two actors completely coated in latex and make-up, two CGI creations and just one human?

"Guardians'" late-summer release date could be a point of concern as well. August has not always been favorable for sci-fi and superhero films, possibly due to audience burnt-out after months of studio tent-pole releases. In 2013, "Elysium" was seen as a mild failure, opening to less than $30M despite a big ad roll-out and Matt Damon's face on the poster. Later that same month, "Kick-Ass 2" performed reasonably well, if substantially softer than the cult hit original. Going back further, in August 2012's "Total Recall" remake flopped with a lackluster $25M opening. Despite studios' best efforts, releasing a movie at the tail end of the summer -- and more importantly, at the end of the summer movie season -- has not always been a profitable venture.

An opening in the $25M-$30M range would be perceived as a complete disaster for "Guardians" when viewed against Marvel's recent track record of first weekend box office domination and record setting; "Thor: The Dark World" opened to $85M last November, and "Iron Man 3" opened to $174M in May.

And it may not matter how good the final product is; critical acclaim doesn't necessarily translate into box office gold. Take 2012's "Dredd," which had stellar reviews and a boatload of online hype leading into its September opening weekend. It debuted to a miserable $6M, and went on to gross only $35M, worldwide.

All of this, of course, is purely speculation. And in all fairness, predicting "Guardians of the Galaxy's" success by analyzing past science-fiction and superhero efforts might be an apples-to-oranges comparison. Despite the challenges "Guardians" faces in terms of putting casual fans in the seats, the movie does sport Marvel's secret weapon: Continuity. In 2008, Marvel began to slowly weave their films together through Easter eggs, post-credits scenes and casual references. Since then, the continuity progressively tightened up, leading directly to 2012's "The Avengers."

In May of 2013, "Iron Man 3" was perceived by many as a de facto sequel to "The Avengers," rocketing its box-office totals north of a billion dollars worldwide. November's "Thor" sequel made nearly $200M more than the original did in early 2011; the link it shares with the greater Marvel Cinematic Universe was no doubt part of its success.

A strong box office performance from "Guardians" would almost certainly prove that Marvel's brand loyalty trumps star power, director clout and familiarity with well-established characters. If you're a fan of Marvel's past films, there is a strong incentive to attend "Guardians of the Galaxy," if for no other reason than, in some way, it will be the next chapter chapter in the larger narrative -- which is not something moviegoers have been willing to miss out on so far.

"Guardians of the Galaxy" opens August 1, 2014 in theaters.