The Tigers selected Farmer's contract from Triple-A Toledo on Sunday, Evan Woodbery of MLive.com reports.
He'll be joining the bullpen as a replacement for Beau Burrows, who was optioned to Triple-A after Saturday's 15-2 loss to the White Sox. Farmer owns an unremarkable 3.97 ERA and 1.35 WHIP at Triple-A this season, but he's been excellent over his last four outings, allowing no runs on three hits and no walks over 6.1 innings.