Michael Nordine author There’s no shortage of great movies about baseball, but there is a severe lack of films about the Negro leagues. The fifth inning of Ken Burns’ expansive “Baseball” covers them with admirable reverence, but feature-length projects — whether narrative or documentary — are vanishingly rare. “The League” is therefore something close to required viewing for devotees of our national pastime just by virtue of its existence, so it comes as a relief that Sam Pollard’s documentary (exec produced by Ahmir “Questlove” Thompson) is also quite good on the merits. Given his résumé, that shouldn’t come as a surprise. Pollard’s prior work as director includes “MLK/FBI” and “Citizen Ashe,” and he’s also edited several Spike Lee joints; in addition to a Peabody Award and career achievement prize from the International Documentary Association, he shared an Oscar nomination with Lee for 1997’s “4 Little Girls” about the 16th Street Baptist Church bombing.