The Tigers will option Holton to Triple-A Toledo on Thursday, Evan Woodbery of MLive.com reports.
Holton appeared to be in decent standing for a bullpen spot throughout most of camp, but he'll end up beginning the season in the minors with the Tigers opting to include non-roster invitees Trey Wingenter and Chasen Shreve in the Opening Day bullpen. The 26-year-old southpaw should be Detroit's top choice for a call-up if the team requires an extra lefty arm out of the bullpen at any point this season.