Stop me if you've heard this before, but their defense will be improved. Replacing the statue of Raul Ibanez in left and rolling Yuniesky Betancourt into shape - or perhaps unrolling - with the addition of Ronny Cedeno is going to help out pitchers like Carlos Silva and Jarrod Washburn.
Bullpen casserole! The Mariners have added Tyler Walker, Luis Pena, David Aardsma, Garrett Olson, and Jason Vargas on major league deals or through trades and has non-roster invitees like Eric Hull, Tyler Johnson, Shawn Kelley, Denny Stark (he's still pitching?), and the best name in baseball: Chris Jakubauskas. Yes, Jakubauskas.
That's not the only fun name on the Mariners. Reegie Corona, Bryan LaHair, Matt Tuiasosopo, Wladimir Balentien, Ryan Rowland-Smith, Marwin Vega, and Callix Crabbe. Not entirely relevant to baseball skill, but I never claimed it was.