The Athletics placed Miller on the 15-day injured list Thursday with right elbow inflammation.
An MRI taken Tuesday on Miller's elbow came back negative for any structural damage, but the A's will play things carefully with the 24-year-old starter. He leaves behind a promising 3.38 ERA, 0.98 WHIP and 22:7 K:BB through his first 21.1 major-league innings. Zach Neal and Luis Medina are joining Oakland's pitching staff Thursday.