According to film noir historian Bill Hare, producer Mark Hellinger first sought out burly leading man Wayne Morris for the male lead in The Killers (1946). Morris had performed in various films as a professional fighter, most notably in the 1937 Warner Brothers release Kid Galahad; but—once Hellinger determined the cost demanded by Warner Brothers to loan out Morris—he looked elsewhere and his gaze fell on a trapeze artist turned theater actor named Burt Lancaster whose raw magnetism had impressed talent scouts during a brief Broadway run of A Sound Of Hunting.
Though Bosley Crowther's New York Times review of The Killers questioned the translation of Hemingway's text to the screen, he noted in passing: "a new actor, Burt Lancaster, gives a lanky and wistful imitation of a nice guy who's wooed to his ruin."
In his essential essay accompanying the Criterion DVD release of The Killers, Jonathan Lethem described Burt Lancaster's character "the Swede" as "a big dumb animal, deep enough to feel pain, no deeper. ...Lancaster, built to defeat a white t-shirt as well as any man, also imbues the animal with existential dimensions by the thwarted intelligence lighting his eyes." At The Onion's A.V. Club, Scott Tobias characterized "the Swede" as "a palooka" and a "lean block of muscles and little else."
The Killers made a star not only out of Burt Lancaster but also out of his female lead Ava Gardner. Even though she'd acted for years in bit parts as an MGM contract player, Gardner was still a relative unknown. Audiences took note, however, of her performance as "Kitty", which—according to Philip French at The Guardian—smoldered "like Mount Etna." It was a fortuitous piece of casting. According to a comment at Noir of the Week, Gardner was offered up by MGM casting director Billy Grady as a substitute choice after Audrey Totter—Hellinger's first choice for "Kitty"—opted for her assignment with Bob Montgomery in Lady In the Lake. Thank God for second choices and second chances! It's nearly impossible to imagine The Killers with Wayne Morris and Audrey Totter as "the Swede" and "Kitty".
According to Ava Gardner's biographer Lee Server, Gardner and Lancaster got along well during production: "She liked Lancaster. He had a great, charismatic enthusiasm for life. At the age of thirty (sic), after many years of struggling on the obscure fringes of show business, he now seemed to be inescapably bound for sudden success." (Ava Gardner: Love is Nothing, St. Martin's Press, 2006, p. 124.) Shortly after Gardner passed away in January 1990, Lancaster exclaimed: "What a warm heart. She was beautiful, sure. But she was wonderful, kind. She used to come down to our house at the beach and play with our kids and cook."