It's My Turn (1980)

Synopsis
Claudia Weill's second feature is a romantic look at the humorous and tragic sides of love, starring Jill Clayburgh as Kate Gunzinger, a mathematics professor who lives with perpetually sunny architect Homer (Charles Grodin) in Chicago. But during a trip to New York City, Kate becomes romantically involved with handsome hunk Ben Lewin (Michael Douglas), a recently retired professional baseball player who is trying to adjust to a life outside of professional sports. The son of her father's fiancee, Ben, in spite of uncertainties about his future, actively pursues Kate, and Kate, much to her surprise, willingly permits Ben to make his amorous approaches. ~ Paul Brenner, All Movie Guide