The opening shot of Michael Mann's masterfully crafted boxer biography "Ali" is an image from behind a punching bag being pounded by the champ in rapid musical rhythm. As the bag flashes by with a strobe-like effect, that intensely focused gaze Muhammad Ali is famous for -- that laser beam look that means he's tuned out the world, that stare as steely as a freight train bearing down on you -- beams out of Will Smith's eyes.

It is the one and only time in the film you'll even remember the star's name, because for the next two and a half hours Smith inhabits Ali -- his power, grace, ego, humor and body language, inside and outside the ring -- as well as any actor could.

Choosing to focus on ten momentous years in Ali's life, Mann's round by round, bobbing and weaving narrative style assumes at least a passing knowledge of the fighter's life, merely dropping in on pivotal events without spending much time catching the audience up on the particulars of who, when and where.

In a leisurely, stylish montage title sequence, Mann includes the punching bag scene and plants the seeds of his subject's political activism in a flashback showing an adolescent Cassius Clay sitting in the back of a bus, staring at a newspaper headline about a vicious lynching. Then the director quickly establishes Clay's early interest in Islam and his friendship with Malcolm X (Mario Van Peebles) before jumping right into the ring for Clay's 1964 championship bout against Sonny Liston.

All boxing movies live or die by their fight sequences, and the visually gifted Mann -- who can even keep you on the edge of your seat with a subject as dull as corporate whistle blowing (see "The Insider") -- shows both his patience and his inventiveness in these defining moments. He lets this first fight play out in near-real time with a minimum of well-placed edits, and in incredibly rich and colorful photography that blacks out almost everything beyond the ring except the arena lights. He takes you inside the ring with SteadyCam shots that ride the fighters' shoulders. Then he gets you inside the fighter's heads with reverberating, grainy flashes of digital video from cameras that must have been piggy-backing on the actors in certain takes. It's an incredible perspective that provides a visceral sense of power in punches both thrown and received.

But while Mann takes the time to feel every punch in the matches he recreates, he darts around so rapidly in other parts of Ali's life that some major characters go unexplored at best and practically unidentified at worst. "Ali" treats the three wives the fighter goes through in the course of this decade as a footnote. Jamie Foxx plays Drew 'Bundini' Brown, a major member of Ali's entourage, but heck if I know what he does. Jeffrey Wright plays Ali's ever-present photographer -- who was also his brother, I think. It's hard to say since the man has only about four lines of dialogue. Of course, garrulous sportscaster Howard Cosell -- perfectly personified by Jon Voight -- gets plenty of screen time since his playfully savage verbal sparring with the champ is the stuff of legend.

Oddly, Mario Van Peebles has several scenes to himself in his strong performance as Malcolm X, in part because the Black Muslim leader's murder was a turning point in Ali's life. The fighter's Islamic faith plays a major role in the film since it covers the years when Ali changed his name from Cassius Clay (it's implied his Muslim name was given to him by prophet Elijah Muhammad as a way of driving a wedge between Ali and Malcolm X), when he spoke out against the Vietnam war, when he lost his boxing license as a result, and when he fought his draft notice all the way to the Supreme Court seeking contentious objector status.

Smith does a brilliant slow burn over the course of the film of Ali's growing ire about these issues and his ill treatment by the white establishment. But what we don't see, conspicuously enough, is how Ali spends the months of his boxing suspension or how exactly he comes close to growing broke.

The picture's last act covers the events leading up to the "Rumble in the Jungle," Ali's legendary 1974 fight against George Foreman, which was remarkably documented in the recent all-access non-fiction film "When We Were Kings" and the very existence of that film poses the biggest problem for this one. Smith may play Muhammad Ali superbly, but the man is larger than life and simply can't be equaled.

If there's a choice between watching someone copy Ali's charisma (and of course, his gift for talking smack and making it rhyme) or watching the champ himself in many of the events recreated verbatim in this biopic -- which would you rather see?