Shoppach was designated for assignment last Friday in order to make room for Henry Blanco, a 41-year-old catcher who was released by the Blue Jays earlier in the week.
Shoppach, 33, hit .196 with three home runs and nine RBIs in 35 games after signing a one-year, $1.5 million contract to be the Mariners' backup catcher in the spring. The nine-year veteran is a career .224 hitter in 571 games with the Red Sox, Indians, Rays, Mets and Mariners.
Blanco hit a grand slam in his first appearance for the Mariners, a 4-0 victory in Oakland on Saturday, and made his second start in Thursday's series finale in Anaheim.
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.