Tatum O'Neal trained with a professional sports trainer for several weeks before filming began in August 1975, so she could get her pitch "pitch perfect," so to speak. Although some of the pitches in the movie were done by stunt doubles, O'Neal did the bulk of them on her own. (Rare for a movie like this,)
The Bears were the only team in the league whose nickname and colors were not borrowed from a major league baseball team. This helped reinforce their status as misfits and underdogs.
Reportedly, star Walter Matthau was paid US $750,000 while Tatum O'Neal was paid US $350,000 and eight percent of net profits.
Jodie Foster was cast at one point as Amanda Whurlitzer but dropped out in order to play Iris in Martin Scorsese's Taxi Driver (1976).