Treinen was placed on the injured list Friday due to right shoulder discomfort, Juan Toribio of MLB.com reports.
Treinen hasn't pitched in over a week, but the transaction can only be backdated by three days, so he'll miss at least one more week. If his injury remains nothing worse than discomfort, it's possible he returns at that point, though a longer absence is certainly possible. Daniel Hudson has already picked up one save this season when Craig Kimbrel was unavailable and will remain Kimbrel's top deputy until Treinen returns.