There are some incredible fight scenes in Benny Safdie's UFC biopic, The Smashing Machine. But all of them are between Dwayne Johnson and Emily Blunt.

There are a couple of spectacular fights in Benny Safide's The Smashing Machine. The new film, about the life and career of Mark Kerr during the early days of the UFC and mixed martial arts going mainstream, is marketed for its hard-hitting sports action, as well as Dwayne Johnson's physical and spiritual transformation. And to be sure, the real-life wrestler with the Goliathian physique does fine work as Kerr in and out of the ring, stretching far beyond his Rock persona.

Yet the cinematic body blows that land hardest come squarely from the film's domestic side. It is when Johnson's Kerr and Emily Blunt as longtime girlfriend Dawn Staples enter a verbal arena that Safdie's movie becomes devastating -- and certainly more exciting than anything occurring inside an octagon. Johnson and Blunt have of course acted onscreen together before, with their faint but tangible chemistry being one of the few bright spots in the literal Disney theme park ride movie, Jungle Cruise. Those of us who noticed that flickering crackle back then can now feel a sense of vindication, as the spark's been fanned into a roaring inferno that leaves both Smashing performances burning bright.

From the outside, Blunt seems cast yet again in the relatively thankless role of "the wife" or "girlfriend," an irony since that Hollywood archetype earned her an overdue Oscar nod after Christopher Nolan's Oppenheimer. She is surely about to receive a second after Smashing Machine, which takes the tired sports drama convention of the athlete and his doting lover to a propulsive place while essaying Mark and Dawn during their tumultuous years between 1997 and 2000.

Early in the picture, one of Mark's several trainers who must be mistaking Blunt for Talia Shire, even tells her to "just take care" of Mark. Perhaps from a distance it would seem a reasonable request. Johnson imbues his protagonist with a paradoxical gentle giant quality that emphasizes an unexpected warmth. It also conceals a deep-seated desire to dominate, both in his bloodsport and in life. This unmistakable ambition collides headlong against Blunt's own brittle shoreline. In this way, Safdie's screenplay probably does walk the razor's edge while flirting with the shrew or "troubled woman" archetype, but Blunt and her director dig beneath the surface, extracting great affection and complexity in a turn that hints at undiagnosed disorders and severe emotional fault lines.