Hernandez was pulled after two innings in Tuesday's 19-9 loss to the Tigers, and he flew back to Seattle for tests that showed inflammation in his right shoulder. The six-time All-Star is 2-2 with a 4.73 ERA in five starts this season after allowing four runs on six hits in his abbreviated outing against Detroit.
A source has told MLB.com's Jon Paul Morosi that Hernandez is expected to be sidelined for at least two to three weeks.
Haniger also was lifted in the third inning on Tuesday after straining the oblique muscle in his right side.