"I respect these guys' preparation that they have going into a game, how they push through things, and try and make something out of nothing at times. If you waited around until you felt perfect, you would never play this game."
Garcia was scheduled to have a second opinion later Tuesday.
Lance Lynn, who pitched three innings in relief and picked up the Game 2 win, will take Garcia's spot in the rotation if the Cardinals advance to the next round.
Miller, one of the top pitching prospects in baseball, appeared in six games this season as a September call-up. He worked 13 2-3 innings with a 1.32 ERA.
Follow Joseph White at www.Twitter.com/JGWhiteAP