The Guardians optioned Allen to Triple-A Columbus on Sunday, Chris Assenheimer of the Elyria Chronicle-Telegram reports.
Allen is the second member of the Guardians' Opening Day rotation to be sent to Columbus within a week, as Triston McKenzie was previously dispatched to the minors last Sunday. Though he's stayed healthy all season, Allen has struggled mightily to build on a solid 2023 rookie campaign, as he's turned in a 5.67 ERA, 1.55 WHIP and 76:35 K:BB across 87.1 innings through 18 starts. He'll cede his spot on the 26-man active roster to newly acquired right-hander Spencer Howard, who could end up entering the rotation the next time Allen's turn comes up Thursday in Detroit.