Bonderman, 30, threw only 252 2/3 innings from 2008-10 and did not pitch at all from 2011-12 due to Tommy John surgery and complications from Thoracic Outlet Syndrome. In his last big-league season, he went 8-10 with a 5.53 ERA in 171 innings for the Tigers.
The Mariners signed Bonderman, a local kid from Washington, to a minor-league contract in spring training. His comeback attempt started in Triple-A, where he went 2-4 with a 4.52 ERA in 11 starts for Seattle's Triple-A affiliate.
Bonderman will be replacing right-hander Brandon Maurer in the rotation. Maurer, 22, went 2-7 with a 6.93 ERA in 10 starts before being sent down this week.