First things first: Adam Kennedy has only been a member of the organization since January. Sean Kazmar, meanwhile, has been a member of the organization since November. And Kennedy has had his own Mariners jersey stitched up.
So whose jersey is this, and why is Sean Kazmar wearing it?
Sean Kazmar has been way more interesting than I ever expected him to be.
Update: best guess is Mike Brumley, who switched his number from 29 to 18. That seems to answer the first question.