Mark Wahlberg (“The Other Guys”) has gone the route of the inspirational, true-story sports picture before, in 2006’s “Invincible.”

Director David O. Russell, however, has not. He’s spent his entire career straying as far as he can from the main streets of convention. That’s what happens when your feature debut (1994’s “Spanking the Monkey”) mines the subject of mother-son incest for laughs.

What’s most interesting about Wahlberg and Russell’s third collaboration, “The Fighter,” is less about it being miles above your traditional underdog story and more about Russell being involved in this kind of thing at all.

Then again, the film is all about second chances, and Lord knows Russell could use one. His last picture, 2004’s existential “I Heart Huckabees,” flopped; he earned a YouTube-fueled rep as an on-set tyrant; he divorced in 2007; and his last project, “Nailed,” has yet to be released, partly because he was forced to shut down production before completion over money woes.

Woe be to the moviegoer who chooses not to snap up ringside seats for “The Fighter,” thinking it watereddown “Rocky.” This is better than “Rocky.” Heck, it makes “Rocky” look like … oh, say, “Rocky V.”

Wahlberg plays real-life boxer Micky Ward; that he doesn’t enjoy household-name status like Mike Tyson is to the film’s and viewers’ benefits. A professional boxer in working-class Massachusetts of the early 1990s, Ward is managed by his overbearing mother (Melissa Leo, “Frozen River”) and trained by his older half-brother, Dicky Eklund (Christian Bale, “Public Enemies”), a former boxer himself forever boasting about that one time in ’78 when he knocked down Sugar Ray Leonard. (Never mind Sugar Ray actually won.)

In his day, Dicky coulda been somebody, coulda been a contender, but he’s addicted to crack, to which his family all but turns a blind eye. Micky’s pretty much the only one willing to face reality; he’s forced to in order to regain traction on a career that has slammed into a rut.

For him, the conflict inside the ring is nothing compared to what he faces daily outside, which is only heightened when his romance with a bartender (Amy Adams, “Julie & Julia”) drives another wedge within the warring Wards.

As a producer of the film, which took four years’ labor to shepherd to screen, Wahlberg has much invested in “The Fighter,” and gives it his all, delivering a fine performance as the grounded, levelheaded brawler who doesn’t pretend the odds aren’t stacked against him. But the title could well refer equally to Bale’s character, even if Dicky doesn’t have the same winning spirit coursing through his veins.

Bale owns every frame he’s in, acting the hell out of Dicky on his way toward an inevitable Oscar nomination he’s currently favored to win. Rail-thin in stark contrast to his buffed-up Batman physique, he’s all nervous twitches and empty swagger as Dicky continues living a lie. The final scene between the two brothers, in the form of a couch-to-camera confessional, gave me goose bumps, even more so than Micky’s expected third-act victory.

It’s this pinpoint-accurate poignancy that gives “The Fighter” its biggest punch.