I mentioned that Brian L. Hunter, accounting for position, had the worst hitting season in Mariner history. His hitting in 1999 was worth -27.5 runs below average and since he was playing left field, he gets docked another 4.5 runs for a combined -32 runs of batting and position. Nobody has ever been worse for the Mariners.
Second on that list though at -30 runs overall is a man who posted a .221/.299/.335 line as a designated hitter in 1991. That man? Alvin Davis.
The first player in the franchise to win a major award, Rookie of the Year in 1984, Davis was an asset at first base from 1984 through '90. But he utterly collapsed in 1991 at the age of 30. He would leave the team after that year, play 40 similarly bad games with the Angels and be done in baseball.
Alvin Davis was a legitimately great Mariner. During his prime seven seasons he averaged right around 3 WAR. Not fantastic or anything for a single season mark, but for a seven-year average, that's not an easy task. Furthermore, he was widely considered to be the first real star for the Mariners and brought some positive attention to the club. In 1997 he became the first person inducted to the Mariners Hall of Fame, since joined by Dave Niehaus, Jay Buhner and Edgar Martinez.
All of that is the good stuff, but there's an end to the story on the field as well, and it was premature and not pretty. However, and maybe it's the nearness to the retirement of Ken Griffey Jr., but finding out about Davis' final season with Seattle strikes an oddly apt tune. Hanging on one too many seasons and finishing up as a downright terrible DH? How fitting, Alvin Davis. Mr. Mariner indeed.