Battle of the Sexes details the events leading up to the much ballyhooed 1973 winner-take-all tennis match (the purse was 100,000 dollars) between women’s world champion Billie Jean King (Emma Stone) and former men’s champ and self-proclaimed male chauvinist Bobby Riggs (Steve Carell), which became one of the most watched televised sporting events in history, reaching 90 million global viewers. The match itself, played at the Houston Astrodome, wasn’t much, as the 29-year-old King (spoiler alert!) trounced the much slower, 55-year-old Riggs in three straight sets. But King’s victory still struck a blow for women’s equality in tennis and beyond, making it a colorful story ripe for great comedy and heartfelt drama. Unfortunately, Battle of the Sexes serves up a double fault: It isn’t very funny and it lacks involving drama. And for a story essentially about tennis, scant time is spent on the court.

The movie begins well enough, with King challenging U.S. Lawn Tennis Association chief Jack Kramer (Bill Pullman, sleazy and sensational) to make women’s tournament purses equal to the payout for the men (which is currently eight times higher). When he refuses, King mobilizes other top female players to boycott and form the rival Women’s Tennis Association. It’s also at this time that King, who is married to her trainer and coach Larry (Austin Stowell), starts exploring her attraction to other women. She meets hairdresser Marilyn Barnett (Andrea Riseborough), and their flirtatious friendship soon explodes into an intimate affair. As for Riggs, he’s desperately looking for a way to stay relevant in the tennis world, while struggling with a gambling addiction that’s threatening to destroy his marriage. When one of his gambling buddies makes an offhand remark that he’d pay money to see Riggs play King, Riggs seizes on the idea and calls her. “Male chauvinist pig versus hairy-legged feminist,” is how he pitches the concept to her. She refuses. Undeterred, he instead calls upon soon-to-be top-ranked Margaret Court (Jessica McNamee), and she accepts because she needs the prize money. But when Riggs defeats Court in straight sets and continues making condescending remarks about women, King realizes she has to play him. And win.

It’s a great story, but directors Valerie Faris and Jonathan Dayton (Little Miss Sunshine), along with screenwriter Simon Beaufoy (Slumdog Millionaire), can’t make up their minds what kind of movie they want to make: an intimate drama, an uplifting sports yarn, or a light comedy. They ultimately try all three, with decidedly mixed results. The first half is predominantly about King’s affair with Barnett, and their relationship is the heart of the movie; Riggs pops up occasionally and adds comic relief, but it feels like he’s in a different film entirely. It also doesn’t help that Stone is off her game here, as her subdued portrayal lacks King’s contagious passion. It’s the least convincing performance the Oscar winner has ever given. Meanwhile, Carell is a delight but he’s underused, particularly in the early going.

When King meets Barnett, the hairdresser tells her she needs a good trim. The same is true of the movie: Scenes drag on interminably, and a good 20 to 30 minutes could have been easily snipped without losing anything of importance. One intriguing subplot that’s left unexplored is the possibility that Riggs threw the match to pay off his gambling debts to the mob (this isn’t particularly believable, but rumors about it have persisted for years). That would have given the film a gut-punch twist—a woman proves her worth, but a handful of men still refuse to believe it—that could have perhaps enlivened this otherwise weary rendering.

The best thing about Battle of the Sexes is its superb supporting cast. Elisabeth Shue is devastatingly good as Riggs’ dignified wife Priscilla; Sarah Silverman is a hoot as King’s manager Gladys Heldman, who serves as the fledgling WTA’s chain-smoking PR point person; Alan Cumming provides great emotional support as a daring fashion designer on the women’s tour; and Stowell delivers a shattering performance as King’s devoted husband, who slowly realizes his wife is drifting away from him.

Given its rich story and the top-tier talent in front of and behind the camera, Battle of the Sexes should have been one of the best movies of the year. Instead, it’s one of the most disappointing, serving up one unforced error after another.