Miller (back) allowed one hit while striking out three across one scoreless inning in Friday's 6-1 Cactus League loss to the Reds.
Miller made his spring debut after missing the first three weeks of Cactus League play due to lower-back tightness. The left-hander surrendered a single to the first batter he faced but went on to strike out the next three, throwing 12 of his 20 pitches for strikes. The 28-year-old's 2025 season was cut short due to a left elbow injury. He posted a 1.50 ERA, 1.47 WHIP and 22:20 K:BB across 30 innings in 36 relief appearances last season.