Keller will be called up from Triple-A Indianapolis to start in Monday's doubleheader against the Reds, Jonathan Mayo of MLB.com reports.
General manager Neal Huntington indicated last week the organization still wanted to see Keller further develop his new slider/cutter, but apparently he's now ready for his major-league debut. The 23-year-old has a 3.45 ERA, 1.43 WHIP and 56:20 K:BB through nine starts with Indianapolis this season.