Miller was promoted from Double-A Midland to Triple-A Las Vegas on Tuesday.
Oakland's top pitching prospect, Miller struck out eight batters in 3.2 innings in his first Double-A start of the season and was subsequently promoted to the Pacific Coast League. He made two starts at Triple-A late last season and will look to put the finishing touches on his minor-league development in the coming months while navigating the harsh PCL pitching conditions.