Headrick was placed on the 7-day injured list at Triple-A St. Paul on Monday with a forearm strain, Brandon Warne of Access Twins reports.
The left-hander presumably suffered the injury during his start against Nashville on Saturday, when he struck out seven across five scoreless innings. Headrick doesn't have an official timeline for his return, but the fact it's an forearm injury likely means he'll be out beyond the 7-day minimum.