Mastrobuoni was recalled from Triple-A Tacoma on Thursday.
The Mariners acquired Eugenio Suarez to handle third base, and Mastrobuoni fits better as a bench infielder role than Ben Williamson, who will head back to Triple-A to get regular at-bats. Mastrobuoni is hitting .252 with one home run and five steals in 71 games in the majors.