I am curious how much of this is drawn from the real-life baseball player(s) it was allegedly based on.
I can't find much to confirm or deny whether Malamud used Billy Jurges as a model, but he would have been 18 years old when Jurges, a short stop for the Cubs, was shot by a show-girl. Most people assume the book was based largely on Eddie Waitkus, who was shot by an obsessed fan early on in his career.
Jurges was shot in '32 and Waitkus in '49. Obviously, Waitkus was famous enough to have stalking fans already and Jurges had won the pennant before he was shot by the showgirl. Maybe it was just a incident that fascinated Malamud enough to work them into his story. Of course, Jurges is more interesting to me as an attorney as he refused to testify against his shooter. She was acquitted and he went on to win more pennants.
I find the initial shooting one of the loosest plot points in the book - there seems to be no good reason for it. Roy isn't famous. Granted, it seems he has leered at her quite a bit. But I find the notion that Harriet was obsessed with just shooting the best player to be a bit... thin.