After the Buffalo Bills of the NFL clinched a playoffs spot for the first time since 1999, The Mariners entered this season with the longest active playoff drought in the four major North American professional sports, failing to make their first postseason appearance since 2001.
The Mariners were eliminated from playoff contention on September 22 with the Athletics win against the Minnesota Twins.
On December 7, 2017, the Mariners traded three minor leaguers to the Miami Marlins for Dee Gordon and $1 million in international slot money.
General manager Jerry Dipoto stated he planned to use Gordon in center field instead of his usual second base.
Infielders Outfielders Coaches (Through September 30, 2018) Players in bold finished the season on the active roster.