Puzzled
Why was Jimmy changing that baby's diaper instead of playing baseball in that field?
Why was that baby crying when Jimmy put her down in her stroller before he got on the field?
His dream was baseball not day care
By that point in the movie, Jimmy had given up hope that he would get a chance to try out, so he decided to change the baby's diaper and head home...Jimmy wasn't on the field because he was trying out as a pitcher and waiting for his turn....
The baby was probably crying because it was hot and she had been there all day and got cranky, plus she needed a diaper change (she was probably wet or dirty)....
Here's a better question...what did Lori do with the baby when she took Hunter and Jessie to the Rangers' game?...the whole town was at the game, including Jim's mom and dad.