I think that E. Santana is a risk of being demoted when Escobar is activated from the DL. The other candidate would be Palmer, but he (unlike Santana) is now pitching well. Weaver, Saunders, and Lackey are not going anywhere. The last rehab start of Escobar would be yesterday (Monday) making his next start Saturday. That just happens to be the day that E. Santana is scheduled to start next. The next start for Palmer would be Friday.
Of course if Santana is demoted, he will lose value in trade. I don't know for sure if he will be, but I definitely think that he might be.
You should be able to pick up a Pavano equivalent on the WW. And it sounds like you really don't need Tejada.
So in my mind the issues are whether you can wait for Santana (including the possibility of a demotion) and whether you can find use for Tejada (including spinning him off in another trade). And what pitching is available on your WW to replace Santana.
I can't give you a definite recommendation here, but these are the issues I would consider.