Emma Stone was initially cast as Billie Jean King, but scheduling issues forced her to pass on the role. Brie Larson was ultimately tapped to replace Stone. After a few months, Larson dropped out. After Stone's schedule was cleared, she was able to take back the role.
The film sugarcoats the tragic love affair with Marilyn. What was private until 1981 became public when Marilyn sued King by invoking the palimony law nearly destroying King's career. It would take years from then for King to rebuild what she'd lost.
Bobby Riggs' training partner and friend Lornie Kuhle is played by Eric Olsen in the movie. The real Lornie Kuhle makes a cameo in the movie playing Pat Summerall, the newscaster seen at the beginning of the match between Bobby Riggs and Margaret Court.