BTB has a post up that looks at the FIP+ of each A.L. West team. What jumps out at you about the Rangers is that Kevin Millwood was better last year (in terms of FIP+) than you would probably expect, and Harrison, Hurley, Feldman, and Padilla were worse.
One caveat here...I think that the three year park factors that are being applied understate the hitter-friendly nature of TBIA (mainly, I think there was a bit of an aberration the previous couple of years that makes TBIA look more neutral than it really is), so I think the park-adjusted numbers may not be quite so bad as they look here.