(Seattle, WA)  --  The Seattle Mariners say former player and broadcaster Dave Henderson has died at age 57.  Henderson died yesterday morning at Harborview Medical Center after suffering a heart attack.  He played for the Mariners organization for nine years after being the franchise's first-ever pick in the Major League draft in 1977, and ended his career with Kansas City in 1994. Henderson also worked for the Mariners as a broadcaster for eleven years.