If you have the nickname of "Mr. Mariner," it stands to reason that the player in question is an important player in franchise history.

Bret Boone would make history as the first-ever third-generation Major League Baseball player when he debuted with the Seattle Mariners in 1992. 

Mark Langston was a second round pick in 1981 and would debut with the Mariners in 1984, where he had a stellar rookie campaign.  The product of San Jose State went 17-10 and would lead the AL in Strikeouts with 204.  He was the runner-up to the Rookie of the Year, coincidentally losing to his teammate, Alvin Davis.

From Venezuela, Freddy Garcia burst on to the scene as a rookie with the Mariners in 1999, where he went 17-8 with 170 Strikeouts and was the runner-up to the Rookie of the Year to Carlos Beltran.  This had to hurt the Houston Astros, who had traded him five years in the Randy Johnson trade after they drafted him as an Amateur Free Agent.