Miller was optioned to Triple-A Round Rock on Monday.
Miller made his final start of the season Sunday against the Angels, allowing seven runs on nine hits and three walks while striking out five in four innings to take the loss. He posted a 10.97 ERA and 2.25 WHIP in 10.2 innings over four appearances (two starts) in the majors this year and isn't guaranteed a major-league role to begin the 2023 campaign.