Keller (shoulder) will begin a rehab assignment Wednesday with Triple-A Omaha, Anne Rogers of MLB.com reports.
Keller might need multiple outings on the farm given that he's been sidelined since May 19 because of right shoulder impingement syndrome. The 27-year-old had pitched to a 4.36 ERA, 1.87 WHIP and 31:40 K:BB in 43.1 innings prior to the IL stint.