Kuntz was struck by a Salvador Perez line drive during batting practice on Monday at Progressive Field.
There's no timetable for Kuntz's return to duty although, even with his arm in a sling, he was going over game plans with players before Tuesday night's game.
Yost said Kuntz is vital during a game in keeping baserunners on the alert at first base as well as positioning the outfielders on defense between each pitch.
"All you've got to do is watch Rusty and he'll put you right there, so it's critical," Yost said.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.