Two and a half stars (PG-13) 

Have you seen the trailers for Leatherheads, George Clooney’s movie built around the early days of professional football? Looks good, doesn’t it? Clooney, Renee Zellweger and The Office’s John Krasinski are appealing leads, the clothing and cityscapes of the 1920s appear convincing, the lighting is spot-on and Randy Newman’s score sets the right tone. The trailer promises a spirited film full of action, snappy dialogue, a little romance, some drama and a lot of laughs.

George Clooney’s third film as director, following Confessions of a Dangerous Mind and Good Night and Good Luck, is primarily meant to be an old-fashioned Hollywood screwball comedy and it sorta works, close enough that those distracted by popcorn bucket maneuvering and text messaging on the sly might walk out feeling sufficiently entertained. But I suspect that viewers devoting their full attention to the screen will feel that Leatherheads doesn’t quite get the job done.

There are difficulties with the characters and some gaps in logic, but the big problem is the script. Duncan Brantley and Rick Reilly’s screenplay struggles to be genuine, but instead comes off as an awkward homage with too many stodgy moments.

The setup: It’s 1925, college football reigns supreme and professional football is a joke, with a hodgepodge of farmers, miners, high school kids, middle-age men — you get the idea — brawling across the field with minimal awareness of the rules. Faced with bankruptcy, Duluth Bulldogs leader and star player Dodge Connelly (Clooney) tries to save the team and legitimize pro football by recruiting college player, war hero and all-around nice guy Carter “The Bullet” Rutherford (Krasinski). An offer of $5,000 a game gets Rutherford’s agent CC Frazier (Jonathan Pryce) to convince his client to agree to the deal. Meanwhile, scrappy reporter Lexie Littleton (Zellweger) has been assigned by her editor (Jack Thompson) to take a hard look at The Bullet. Rutherford achieved hero status by single-handedly capturing an entire German regiment, but the editor finds the story suspicious.

That’s all you need to know. Obviously, there will be a romantic triangle. Doubtlessly, Lexie will be put off by Dodge and the two will exchange insults for a while. Most certainly the truth will be uncovered at a particularly disadvantageous time. I have no problem with such plot conventions. I wanted to have a great time at this movie — I expected to have a great time at this movie. But Leatherheads doesn’t maintain a tone. Too often, the snappy dialogue sounds mechanical. The forced screwball comedy is interrupted by slapstick gags that feel like they came from a different film. Then the screwball approach is set aside as the screenplay goes into Frank Capra mode.

George Clooney gives it the college try as director and the cast is game, but there are problems. Dodge is a manipulative creep, though Clooney makes him nominally likable nonetheless. Renee Zellweger winces too much, coming off more like a cranky writer recovering from the mumps than a tough-as-nails reporter. John Krasinski is charming and a bit goofy — a nice combination — but his character is passive for most of the movie.

Leatherheads is entertaining, but given the talent involved, it should have been entertaining and memorable.