I hate to be the blasphemous one but...
Ortiz ain't getting any younger, and in my opinion he is falling off. Further, he no longer has Manny protecting him and upping his quality at bats.
Which leads me to believe that the PR nightmare of rotating the DH around Teixeira, Youk, and Lowell until Lowell's contract is up might also be an alternative, with Ortiz going elsewhere...