The film she struts and swaggers through is a composite and a provocation too. Directed by John Sayles acolyte Karyn Kusama, Girlfight takes the creaky boxing genre, with its tale of the downtrodden outsider seeking redemption in the ring, and by the gimmicky device of switching genders nearly pulls the battered premise off the canvas. Without Rodriguez in the lead, however, and without Kusama's laid-back, quasi-vérité direction, Girlfight might have hit the deck in the first round.

Instead, it's impossible not to pull for Rodriguez's sullen misfit even at her most irascible, as she is in the opening scene. Perched on the windowsill of the girls' lavatory at school, she's disgusted when big-haired buddy Marisol (Elisa Bocanegra) wimps out in a confrontation with the girl who's screwing her boyfriend. Diana has no such qualms about getting physical, and her subsequent brawl in the corridor earns her another trip to the principal's office and another call to fed-up father Sandro (Paul Calderon). Hostile, friendless, and motherless, Diana drifts between explosions of rage and fits of listlessness until Sandro has her drop by the local gym to pay Hector (Jaime Tirelli) for giving her brother Tiny (Ray Santiago) boxing lessons.

What exactly Diana sees in the laboring bodies there is a mystery. When Kusama cuts to Diana's face, we see that, for the first time, she's smiling. Whether at the boys' dreams of glory, their physical exhilaration, the naked aggression and pain, or the sleek abs and puggish profile of Adrian (Santiago Douglas), the gym's rising star, is hard to say. She certainly gets a lot more out of the gym than Tiny, a non-athlete whose real goal is to be a clothes designer (a version of Tiny's tale can be seen in the upcoming Billy Elliot, which uncannily mirrors Girlfight in plot and sexual politics).

When Diana predictably solicits the gruff but fair-minded Hector for lessons of her own, he shapes her raw talent and desire with mind-numbing workouts and philosophical tips. Problems inevitably arise: out of fear of her father's reaction, she takes her lessons on the sly (actually she takes Tiny's lessons), and dad's disapproval looms just as she's about to fight her first boy. It's no surprise either when Diana and Adrian get into a clinch outside the ring -- but Kusama audaciously combines the conventions of the boxing and the romance genres and turns them on their head. In one of the weirder resolutions to a romantic entanglement, Diana and Adrian work out their love difficulties in a featherweight championship bout.

As a hardhitting film about class and racial and sexual conflict, Girlfight too is in the featherweight class. This is no Raging Bull when it comes to raw emotion or graphic fight footage. Despite the location shooting in Brooklyn's Red Hook district (which captures the feel and fetor of hard lives lived in harder places), the film doesn't establish much of a social context. There are colorful locals hanging out at the gym; there's some lip service about escaping from the benighted neighborhood and some half-hearted squabbling about whether girls should be in the ring at all, let alone fighting with boys. But these conflicts are mere shadow boxing. The neighborhood Kusama is most familiar with is Hollywood, the formulas and clichés that shape our entertainment and perhaps our perception of the world. And at times she succumbs to the obvious and unsatisfactory in her reworking of stereotypes (the back story of Diana's mother's death and Sandro's culpability in it is especially weak). For the most part, though, her rewriting and recasting of a familiar script illuminates. And Rodriguez's Diana, as tough and alluring as her goddess namesake, taking punches as well as she dishes them out, is a champion whom women and men alike can cheer.