As you apparently have suggested yourself, the sticking point is that the worst-case scenario is too steep -- you simply cannot let go of such key pieces of the roster, moreover, pieces whose contracts you control for some period of time yet, ignoring the chance that next off-season the budget could be held hostage as Alou did or the chance that you would have to deal him in a fire sale (reduced cost) transaction... the best-case scenario -- that Tejada would hit 30 HRs, steal 30 bases, and bat .300, or something like that -- doesn't get us to the World Series by itself. So, failing an agreement for Tejada to forego that collective bargaining right, just DON'T do it.
Oh, and don't trade Taveras for a one year rental on Contreras, either.
Instead, load up on the alternatives for #4 and #5 starting pitchers to the degree that you can.
(You SHOULD HAVE signed an adequate starting pitcher in free agency long ago -- someone like a Tomko or an Elarton or even an Ortiz. I even would have looked hard at Borowski if either Qualls or Wheeler wanted to take a shot at returning to their starting pitching roots. But don't make it worse now by trading someone unless it is one of those rare, can't-go-wrong deals that another team makes out of dire anxiety/necessity.)
Stick to this current roster until you have some solid evidence from which to judge if Baggy plays first or not. Once you have that, then maybe we can look to prey upon Spring Training jitters that some number of GMs will get in order to swing an advantageous deal.



