Fien signed a one-year, $1.1 million deal with Seattle as a free agent in December.
Fien has a career record of 17-17 with a 4.29 ERA in 299 appearances with the Tigers, Twins, Dodgers and Mariners.
He was 0-1 with a 3.38 ERA over 5 1/3 innings in five appearances with Tacoma this year.
Mariners acquire Bonnell
• The Mariners acquired Minor League right-handed reliever Bryan Bonnell from the Rays on Tuesday in exchange for their International Signing Slot No. 71. Bonnell, 23, is 0-2 with four saves and a 4.09 ERA nine appearances for High-A Charlotte.
Greg Johns has covered the Mariners since 1997, and for MLB.com since 2011. Follow him on Twitter @GregJohnsMLB and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.