One of the cardinal rules of any sports film is that the actors portraying players need to be convincing in that sport, and the that filmmaker must know how to storyboard, block and edit surfing or soccer, golf, baseball, football or basketball into a convincing facsimile of how the game is played.

“Sweetwater,” a drama about one of the players who helped integrate the National Basketball Association in 1950, puts what look like rec league teams on the various courts — a bunch of Dad-bod white guys — and expects us to accept them as the pioneers and first gen stars of the newly-formed NBA.

The early Harlem Globetrotters, a team the NBA dared to play (and lose to) in those segregated formative years, come off a little better — sort of “Eight Men Out” (two-thirds-speed) basketball clowns on their way to becoming the first global ambassadors for hoops.

But in recreating the literal barn-storming nature of America’s fourth or fifth favorite sport of the day, composer turned writer-director Martin Guigui shows no feel for the game or the medium he’s depicting it in in a cumbersome, clunky film that suggests “last kid picked to play” bonafides, or lack thereof.

Screen newcomer Everett Osborne plays Nat “Sweetwater” Clifton, a star Globetrotter picked to be the guy who integrated the NBA in the late ’40s, a World War II veteran who faced racism within the league heirarchy and from fans as he sought to break “the color barrier” in the infant (two stuggling leagues merged and became the NBA in 1949) pro basketball association.

That’s the way the story presents it, anyway. The first Black player signed was someone else, as was the first Black player to take to the court.

The film is framed within a sports reporter (Jim Caviezel) stumbling into a Chicago cab in 1990, and hearing Sweetwater’s story from the man himself — who spent his post-NBA years as a cabbie, marveling at Michael Jordan and remembering his place within the league’s history.

The flashback yarn that Sweetwater spins takes us back to the bus-riding, segregation-hampered early Harlem Globetrotters, scraping by on owner, coach and bus-driver Abe Sapperstein’s (Kevin Pollack) meager payouts, playing assorted local teams in gyms and barns in states where the ‘Trotters couldn’t get a restaurant meal or a hotel room for the night.

But the Globetrotters turned a corner when they played and beat the new pro-league’s best, the Minneapolis Lakers, in Feb. of 1948. Sapperstein sees it as skills and racial equality validation, and as the game that will “make” his team’s reputation and turn it into a global operation, which indeed it did.

NBA figures like New York Knicks coach Joe Lapchick (Jeremy Piven), his boss, Madison Square Garden chief Ned Irish (Cary Elwes) and perhaps even NBA commissioner Maurice Podoloff (Oscar winner Richard Dreyfuss) could see “the future” in this more entertaining, improvisational, individual skill sets (“Black”) style and an integrated league.

Like the Ben Affleck movie “Air,” this is a true (ish) story about a pivotal moment in NBA history, when the league is in jeopardy and a Black star is seen as its salvation.

But as most of America is segregated in the late ’40s, and even rural New Yorkers (Eric Roberts plays a filling station-owning racist) could be relied on to drop the N-word to assert their supremacy. This was never going to be easy.

One interesting thing this script does is keep the racism off the court. Maybe the refs whistled down Sweetwater — named for his taste for sugary beverages growing up in Arkansas — for something that the movie says hadn’t been named “dunks” yet. But the white and Black players seemed to have no issue with integrating the game.

What little conflict there is in the script comes from Sweetwater’s pay beefs with cheapskate owner Sapperstein, who isn’t so bothered by that that he won’t drop a “Nuremberg” reference to any racist who insults his players, and the arduous arguments about integration held in league meetings, with only the Fort Wayne, Indiana owner/coach really going all-in on the racism thing.

The bigger shortcoming is how the film, like the games it painfully recreates, stumbles along at half-speed.

“Sweetwater” has interesting history to teach us, but it does so in a flat narrative that lacks pace or much in the way of charismatic sparks. “Race,” the recent Jesse Owens movie, and “42,” about Jackie Robinson, were similarly-themed and just as old-fashioned but boasted big budgets and bigger names among the supporting players. And formulaic as they were, their scripts had a bit more heart and spark.

“Sweetwater” had promise in conception, but that promise disappeared in the screenwriting long before the screenwriter directed his own script into a near coma.

Rating: PG-13 for some racial slurs, violence and smoking

Cast: Everett Osborne, Jeremy Piven, Cary Elwes, Eric Robert, Jim Caviezel and Richard Dreyfus

Credits: Scripted and directed by Martin Guigui . A Briarcliffe release.

Running time: 1:54