Sports movies have been commonplace since the earliest days of cinema. Over time, however, the general plot outlines has devolved into near stereotypes. Usually, a gutsy athlete (pick a sport) faces a crisis of some form: debilitating illness, romantic dilemma, conflict with the coach/mentor, and so on. The subgenre of the boxing movie is still best exemplified by Martin Scorsese's Raging Bull (1980) and the original Rocky (1976), the fairy tale of the little fighter who could. Finding an innovative manner in which to invert these tales remains the challenge for filmmakers. Director Karyn Kusama, a former assistant to indie stalwart John Sayles, has seemingly found a way by opting to make her protagonist a young woman, thereby providing a fresh outlook on the world of amateur boxing in her highly praised Girlfight. Although Kusama attempts to inject new life into a rather moribund genre, there is only so much she can do. Building the story around Diana (Michelle Rodriguez), a high school student with a temper problem and a troubled home life, is one of the few original touches in the movie. In general, Girlfight succumbs to the conventions of its type with countless scenes of Diana training in the gym and sparring. She has to overcome several obstacles to finally prove herself and her worth, like dealing with the root of her anger -- a domineering father (a well-cast Paul Calderon) who literally drove her mother to suicide. Like Rocky Balboa, she has her own Adrian (an impressive Santiago Douglas), in this case another amateur fighter. Although the plot is rather thin, Diana's journey is captivating for viewers primarily because of the galvanizing performance of newcomer Michelle Rodriguez, emerging as a bona fide movie star. Although untrained, Rodriguez, whose previous screen credits included extra work, makes the character's transitions from an immature, angry child to a confident young woman believable and ultimately moving. Without her, the story would have turned to mush. Her charismatic turn elevates Girlfight to whatever level of art it achieves. There are also fine supporting turns from Ray Santiago as Diana's brother Tiny, who harbors dreams of attending art school, and Jamie Tirelli in the Burgess Meredith role of coach and mentor to Diana. As a writer Kusama still has a way to go, but as a director, she is on surer ground. Although she does have a tendency to allow scenes to run too long, there is promise to her work, best exemplified by the casting and the performances she elicits. While it does have flaws, Girlfight remains engrossing thanks to its leading lady. Rodriguez exhibits a great deal of promise; whether she will be able to build a career still remains to be seen.