Coleman was optioned to Triple-A Omaha on Sunday.
Coleman surrendered four runs over his last two outings and will now head to the minors. Overall he has a 4.02 ERA, 1.53 WHIP and 21:15 K:BB across 15.2 innings this season, and he could rejoin the big-league club later in the year. Brady Singer, who is starting Sunday against Minnesota, was promoted from Omaha in a corresponding move.