And then the wave rolled back: after The Insider, in all its outsized magnificence, Michael Mann has never again made a film of such caliber. An indication of the state where he career landed itself in the '00s can perhaps be squirreled out of the fact that for his 2001 follow-up (the two-year gap between movies was the shortest wait for a new Mann film since 1983 - perhaps another indication), he took up a project that had been wandering around in development hell for the better part of a decade: a monumental, epic-sized biopic of boxer and activist Muhammad Ali nΓ© Cassius Clay, written by Stephen J. Rivele & Christopher Wilkinson, the team responsible for Oliver Stone's Nixon. Mann and his new best buddy Eric Roth picked up the script, shaved it down a bit (it originally spanned Ali's life from childhood into the 1990s and his struggle with Parkinson's), and tailored it a bit more to the themes Mann found especially interesting. And that is how we have Ali, starring Will Smith in the title role, a solidly-crafted film of little particular interest, undone by its ruthlessly standard biopic screenplay.

Even without knowing that the writers also had their fingers in the Nixon pie, that film was already a clear point of reference for how the story plays out in Ali; and whereas Roth's touch was almost totally invisible in The Insider, the later film bears all of his distinctive fingerprints. The problems with Ali's screenplay are not few, but the worst are that, like Nixon, it darts forward from event to event without any sort of context, leaving us to wonder where in time we are; while like Forrest Gump and The Good Shepherd, it is guilty of a very clumsy attempt to marry its narrative to the course of 20th Century history, resulting in a kind of Greatest Hits parade of famous events and people. From Mann, we get only the focus on Ali's code of honor, and how his religious and political beliefs and race activism led him to sacrifice his career as a heavyweight superstar on the altar of protest against the Vietnam War.

Ali's story is one of the great American biographies of the last 100 years, but Ali squanders it by meandering around in search of the angle it wants to take, without ever selecting one: is it to be the story of a man and his beliefs? Or the story of an icon and what he represented? A history of America, 1964-'74, or the history of a man who rose from anonymity to worldwide celebrity? As usual, Mann tinkered with the film quite a lot after its theatrical release, and the director's cut - the only version I've seen - allegedly focuses a great deal more on the political climate of that period than was initially the case. Judging from the generally ambivalent reviews the film received in December 2001, I doubt that leaving it alone would have been much of an improvement.

If I may share a conversation I took part in not that long ago: the first gentleman suggested that Ali was not a tremendously successful movie because Muhammad Ali was not a tremendously interesting person. The second gentleman and myself quickly set him straight: Malcolm X, Vietnam, triumphant black man during the civil rights movement, winning against George Foreman despite being too old to be a proper boxer. "Well," said the first gentleman, "maybe it's just that they didn't do a good job of making that interesting." Precisely. And that pains me to even think, for this should have been a cakewalk of a film for a director with Michael Mann's preoccupations.

It is not the case as it was with L.A. Takedown, that Ali suffers from the director's inattention and indifference, though by the same token, Ali does not boast a surplus of Mannly notes. The opening sequence is without question the most stylistically innovative and challenging part of the whole movie, in which Ali's - then Clay - public boasting about his upcoming match against Sonny Liston (Michael Bennt) is contrasted with his strenuous private training, and then further contrasted with Ali's idol Sam Cooke (David Elliott, in a tiny but marvelous act of mimicry). This is tremendously exciting stuff, worthy of Mann's experiments in cinematic formalism throughout his career: the gliding camera and studio polish of the Sam Cooke moments and the jostling energy of the scenes with Clay surrounded by throngs of reporters and the bleached-out, grainy shots of Clay running, all form a marvelous little snip of cinematic chamber music that makes it seem, briefly, that Ali is going to be Mann's most innovative narrative yet.

Then it goes away - unless you count "disjointed" and "borderline incoherent" as a narrative innovation; me, I'm happier to think of it as the work of a director saddled with an impossible screenplay and not terribly interested in figuring out ways to make it work, when his energies could be spent elsewhere. "Elsewhere" is the fighting sequences (which like all boxing scenes in movies post-1980, owe quite a debt to Raging Bull, though Mann adds more of himself to Scorsese than most filmmakers do), and honestly not much else that I can tell. Though the film is altogether handsome - it had better be, having been shot by Emmanuel Lubezki - it's handsomeness isn't in service of anything. I find myself reflecting on the difference that it describes between Lubezki and Mann's customary cinematographer, Dante Spinotti: Lubezki is much my favorite between the two, but he doesn't gel with the director nearly as well as Spinotti did, and when Spinotti used grain-heavy stock or overexposure or nimble focal tricks, it felt right. When Lubezki does those things, it jars a bit, as those techniques are not a well fit with Lubezki's typically rich imagery.

And so we have a film that is more than competently mounted, with technical wonders to be found all about, but a hollowness just discernible in its core, as though Mann never figured out what it was all supposed to add up to. That wasn't a problem in The Insider, where every moment of the film added to the sense that we were watching real men locked inside a modern myth, and it was something of an anti-problem in Heat, where there was so much stuff being added up together that the movie suffered from pronounced bloat. Ali feels like the first draft of whatever film Mann set out to make, and I think at times I can see the film he had in mind - it's about a man defining himself according to his politics, and letting that definition trump his desire to be successful and famous; but I have to meet Mann much more than halfway to get there. And even so, that doesn't address the fact that unlike every other Mann film, even The Keep, form and content are not all of a piece, here: an idea crops up, is executed, and then just sits there not tying in to anything else.

The saving grace of the film is Will Smith, giving the best performance of his career - can we step back a moment, by the way, and reflect upon how often Mann seems to get career-best performances out of actors, good and bad? And then stop sniffing at him as a "style first" technician? - in a buoyant and angry turn that captures all the myth of Ali without depriving him of humanity in the process. It's a better performance than the movie rewards; it might even be a better performance than the movie requires. I wonder if, absent such a strong, living central performance, it might have been easier to see the film as a series of impressions of Ali's life, and less of a failed conventional biopic. Other than Smith, the cast is not among Mann's strongest, with only an unrecognisable Jon Voight giving a truly great performance as Howard Cosell, here recast as a kind of wise leprechaun, whispering memento mori into Ali's ear at the height of his fame.

It is a disappointing film; that is that. Not the last disappointing film of Mann's career, either, I'm afraid to say. Perhaps he had run out of things to say, between Heat, the story he'd been nurturing since the earliest years of his directorial career, and The Insider, an achievement so complete that nothing could reasonably stack up after it. One can see a great filmmaker trying to break out of Ali, and that is both reassuring, and yet all the more frustrating; but as far as biopics go, at least this one has the spirit of an auteur about it, even if it does not have much in the way of concrete success.