Schooler became Seattle’s bullpen ace in the second half of 1988, saving 15 games and striking out better than a batter an inning. He surpassed that performance in 1989, his first full season, improving his control and finishing third in the AL in saves, trailing only Jeff Russell and Bobby Thigpen. He was on pace for an even better season in 1990, but shoulder stiffness forced him to miss the final month.
Schooler ended up posting thirty saves, good for eighth in the league, but the shoulder injury lingered, and forced him to miss the first half of the 1991 season. He returned July 12 and recorded seven saves, but his arm was never the same. In 1992, he allowed seven home runs, all of which tied the game or put the opposition in the lead. This resulted in a 4.70 ERA, by far the highest of his career. The Mariners let him go following the ’92 season, handing the closer job to Norm Charlton.