Silseth was diagnosed with right elbow inflammation after undergoing an MRI on Wednesday, Rhett Bollinger of MLB.com reports.
The diagnosis comes as good news, as Silseth has been cleared of any ligament damage in his pitching elbow. The right-hander will still need some down time to let the inflammation calm down, so his stay on the injured list could last longer than 15 days. The Angels have moved Jose Soriano into the rotation to fill in for Silseth.