Farrell was placed on the 7-day injured list at Triple-A Iowa on Wednesday with an unspecified injury, Tommy Birch of the Des Moines Register reports.
Farrell has made six appearances (four starts) in Iowa this year and has posted a 4.63 ERA and 1.47 WHIP in 23.1 innings. He gave up four runs in 4.1 innings during Saturday's start and is apparently dealing with an injury that will force him to miss at least a week.