The Mariners used 34 pitchers out of the bullpen over the season. That tells you just how bad their 2019 bullpen must have been.
Brandon Brennan, a rule 5 draft pick the Mariners picked up last year, was the only arm that began the season in the Mariners bullpen and ended the season as well. As a rookie, he had a more solid season than his ERA of 4.56 shows. The ERA is misleading as most of his runs given up were just before he went on the injured list on June 14. He only returned briefly in August than was activated again on September 1.