Shields started and won Sunday's AL Division Series clincher against the Angels and he would be on normal rest should he get the start on Friday.
"Friday is Shields' fifth day, so I imagine he'll start Game 1," Yost said. "What we do in these situations is we get together as a staff, our front-office baseball people, and we discuss it. We haven't had an opportunity to do that yet to see how it's going to match up.
"I'm almost certain Shields will start Game 1, because he'll be on regular rest, ready to go."
The Royals had Monday off but will hold workouts at Kauffman Stadium at 2 p.m. CT on Tuesday and 11 a.m. CT on Wednesday, before departing for Baltimore.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.