From “Philadelphia Story” through “Dumb and Dumber,” one of the most tried-and-true cinematic formulas is the competition between two men for the same woman. Another is the ragtag underdog sports team that goes up against a bigger team that’s all brawn and no heart. “Leatherheads,” which stars and was directed by George Clooney, smashes those two threads together and drags them to good effect through the rollicking early days of professional football.

One of the men in the equation is Jimmy “Dodge” Connelly, a 40-something football player and veteran of the Great War who loves the game and has no other skills. He’s a scrapper on the field who wants the game to succeed without succumbing to encroaching professionalization and niggling rules that forbid his favorite dirty plays. Connelly has the good luck to be played by Mr. Clooney, a matinee idol in the vein of Clark Gable and Cary Grant. A guy like Mr. Clooney always gets the girl. It’s in his DNA, and in the girls’, too.

“Leatherheads” opens in 1925, with Connelly stalking around on the field with his team, the Duluth Bulldogs. The Bulldogs have names like Curly, Hardleg, and Stump. They are rowdy and ruddy; they come from the mines, or straight from high school. “This isn’t exactly the cream of America’s workforce,” Connelly says, and he should know. When the team loses its sponsor and goes bankrupt, he ends up in the unemployment office with charm but no skills — and charm doesn’t put bread on the table outside of Hollywood. Mr. Clooney sticks to period screwball delivery, much as he did as the lead in the Coen brothers’ “O Brother, Where Art Thou?”; he doesn’t wink at the audience — or rather, he never stops winking.

Enter the rival: Carter “The Bullet” Rutherford (John Krasinski) is the top man on Princeton’s football team, a whiz on the field who also happens to be a “Sergeant York”-like war hero adored for single-handedly forcing a few dozen German soldiers to surrender on the battlefront. Now a nationally known heartthrob represented by a smugly slick agent (Jonathan Pryce), Carter endorses razors and Barbasol but keeps mostly quiet about his deeds in battle.

In his role as Jim on the American version of the sitcom “The Office,” Mr. Krasinski plays the big man on the corporate campus. But since there is no cigarette-voiced man’s man to challenge him in the cubicles, he ends up with the girl and the viewer roots for him all the way. Mr. Krasinski uses the exact same goofy smiles and aw-shucks line-readings here, but in contrast to Mr. Clooney’s gravelly adulthood, they make the Bullet seem merely callow. In a way, it’s a measure of how far romantic comedies — and, to be grandiose, romantic aspirations — have fallen that the hero of the contemporary “Office” is the bound-to-lose Baxter of “Leatherheads”: We now prefer boys to men.

The rivalry commences when Connelly quickly ropes Carter into putting Princeton on hold and joining the Bulldogs for an astronomical salary of $5,000 a game. The new star immediately draws huge crowds, and the team starts winning thanks to Carter’s Ivy League playbook. Meanwhile, Connelly and Carter are trailed by a Chicago newspaper reporter, Lexie Littleton (Renée Zellweger), whose editor smells a rat in Carter’s Golden Boy shtick. Soon, the impeccably tailored spitfire is cozying up to both men, though it’s unclear if she’s using her affections to get the story, or just for sport. As Connelly quips of Littleton, “The only thing you hate more than men making a play is when they don’t make a play.”

Honed by 21st-century gym equipment, Ms. Zellweger is a bit slim and hard-edged for the demands of her foxy-reporter role, but her eyes twinkle ably. She and Mr. Clooney have a natural rapport that buoys them along even when the movie’s pacing lags. Mr. Clooney showed off these skills with Catherine Zeta-Jones in the witty and underrated “Intolerable Cruelty” (2003), another screwball comedy by the Coens, this one set in contemporary Beverly Hills. The “Leatherheads” script, written 16 years ago by Duncan Brantley and Sports Illustrated columnist Rick Reilly, does lack zip in some places, which is no small problem in a film whose comedic ancestors were bursting with wit. But the cast is game, and delivers every line as if it were a real zinger. When the movie drags, Randy Newman’s old-timey, ragtime score keeps up the pep, and if it’s a bit of a stylistic jumble in the end, it’s still great fun to watch “Leatherheads” hurtle along through train cars and motorbikes, speakeasies and muddy Midwestern stadiums, from the sumptuous lobby of Duluth’s Ambassador Hotel to the Chicago Daily Tribune newsroom. It’s a bit slick in some places, slack in others, but that’s the film’s point about football, too: Sometimes following the rules takes the fun out of things.

Ms. Graham is an editor at Domino magazine.