The Phillies reassigned Mitchell to their minor-league camp Monday, Todd Zolecki of MLB.com reports.
Mitchell boasts 171.1 innings worth of MLB experience, but with no appearances since 2018 and no openings in the Philadelphia rotation, the 29-year-old wasn't a serious candidate to make the Opening Day roster. He'll likely head to Triple-A Lehigh Valley to begin the 2021 campaign.