The Tigers released Guenther on Friday.
Guenther made nine appearances for the big club in 2025, but he's spent all of 2026 at Triple-A Toledo after losing his spot on the Tigers' 40-man roster over the winter. The 30-year-old lefty posted a 5.40 ERA and 1.73 WHIP across 16.2 innings over 12 appearances with Toledo before hitting the 7-day injured list May 6 due to an unspecified health concern.