Patty Duke missed the audition. Duke would live it vs. "act"
I know Field crawling around on the ground with her new found inner discovery was impressive to most, but it was manufactured. Duke would had gone to a deeper level ,like she has done in other times. Field's projection comes from her lungs, while Duke's comes from her gut. (to paraphrase Mia Farrow as a metaphor: "this is no nightmare, this is really happening!")
Field was fine with the lighter elements and her display of innocence, but the heavy drama is out of her depth. Not a bad performance, but overrated. Not do i think Streep could have done it.