The plot has been done a million times over, and there's nothing new or fresh here to make it worth a viewing. It's almost as if the idea of baseball was oddly worked into the story so that the film could have a title.
Michael Peterson really backed himself into a corner by pairing a child protagonist with an invincible villain, which results in an uninteresting game of cat and mouse with no realistic consequences.
The performances of literally everyone besides Ironside leave much to be desired, ranging from mediocre to ridiculously terrible.
Not much else to say, really. With a short run time of an hour and a half, at least Knuckleball moved at a decent pace and was over quickly.