The Seattle Mariners began as an expansion team in 1977, and like many expansion teams, they took their lumps in the beginning. It took them until 1995, where they would not make their first playoff until 1995 with a team comprising of Alex Rodriguez, Ken Griffey Jr. Randy Johnson and Edgar Martinez, the sky seemed to be the limit, and they would make the playoffs in 1997, 2000, and 2001, but they were unable to win the American League Pennant.
To date, the Mariners are the only Major League Baseball team that has not participated in a World Series.
This list is up to the end of the 2020 season.
Note: Baseball lists are based on an amalgamation of tenure, traditional statistics, advanced statistics, playoff statistics, and post-season accolades.