Slapstick meets screwball in “Leatherheads,” an amiable valentine to an era of breakneck repartee, bathtub booze and anything-goes gridiron warfare.

The setting is 1925 Duluth, Minn., home base of the Bulldogs, a rough-and-ready pro football team in an era when pay was low, glamour was nil and rulebooks were rarely consulted. The only audience at the Bulldogs’ practice field is a bemused cow, and the turnout for their games is scarcely larger or more enthusiastic. Dodge Connolly (George Clooney), the team’s irrepressible quarterback and manager, boosts the game’s entertainment value with bizarre plays like the Rin Tin Tin: The left wide receiver howls like a scalded hound while you snap the ball right.

Still, the crowds are thin, and the team is so cash-strapped they shower in their uniforms to save laundry fees. When Princeton football star Carter “‘The Bullet”‘ Rutherford (John Krasinski) plays his final college game, Dodge entices him to join the teetering Bulldogs for a percentage of the gate, promoting him as the sport’s first superstar. Not only is he a lightning bolt on the field, he’s famed for capturing a platoon of German infantrymen single-handed.

Following Rutherford is Lexie Littleton (Renee Zellweger), a feisty Chicago Tribune reporter ostensibly covering “The Bullet’s” career, but actually investigating his story of battlefield heroism. Soon the Ivy League golden boy and the aging roustabout are romantic rivals, grappling for Lexie’s heart like a mud-slicked pigskin.

Clooney radiates rakish charm, making himself the butt of jokes about his advancing age and including a comic stunt that echoes his recent motorcycle accident. And those endless comparisons to Cary Grant are deserved. Look at the way he uses his eyes in the scene when he first catches sight of Zellweger in a hotel lobby. They have a great rapport; their sharp-tongued comic banter feels effortless. There’s a hint of Marx brothers madness in one scene as Dodge and Lexie, squabbling in a double-berth sleeping car, snap the curtains open and shut as they try for the last indignant word.

Krasinski is solid as a straight arrow with troubling memories, although he never measures up as serious romantic competition. Jonathan Pryce adds suave menace as Carter’s unscrupulous agent, and Stephen Root makes off with most of his scenes as a tippling sports reporter.

“Leatherheads,” Clooney’s third outing as a director, extends his range beyond the showbiz absurdism of “Confessions of a Dangerous Mind” and the political drama of “Good Night and Good Luck.” Clooney, who co-wrote the film, is unabashed in his affection for period Americana and old-school filmmaking, and recreates it with impressive technical polish. He fills the screen with quaint Tin Lizzies and raccoon coats and paces his chat-a-tat-tat dialog scenes with Roaring Twenties momentum. The score is an upbeat blend of vintage tunes and new ragtime from Randy Newman.

Still, Clooney missed one crucial lesson from 1930s comedies: Keep it short. At an hour and 54 minutes, “Leatherheads” often lopes when it should race, with dead-weight scenes and extraneous subplots. The anachronistic dialogue sometimes feels exhumed rather than adapted for modern audiences.

Drawing from movies rather than life, “Leatherheads” often feels like a likable exercise in retro style rather than a film with a compelling reason to exist on its own.