Per Mark Sheldon's Blog:
Generally speaking, you only use three starters in the first round. We won’t try to guess who’s not [in] but that’s a pretty good ace in the hole if you’ve got a guy getting hammered. You usually don’t let guys stick around to get hammered. It’s not like a regular season game.”
Although Baker did not say specifically, it would appear that Homer Bailey is that ace-in-the-hole.
“That is always the toughest part – who do you leave off?” Baker said. “I’ve seen guys get angry. I remember one time with Lasorda, there were a couple of guys upset with him.”