Not sure on this one…it's not a big win for either side really. 

Mariano's career has to be winding down.  I like Montero a lot as a young up and coming catcher…You're giving up the only young guy here in Montero. 

I'd have to agree with the other fellows above on this one.  You basically are looking at trading catchers.  With both relief pitchers at the end of their respective careers, and this being a keeper league, AND the ability of savvy owners to snag saves off the waiver wire EVERY year, the RP trade off here is not really a consideration.

As far as the catchers go, granted Montero is younger, but so much more unproven than Martinez.  In fact, Montero has had only one decent year, and that was based on only 425 AB's.  Martinez, on the other hand, in his 6 seasons of 450 AB's or more, outproduced Montero every single time.  So you have one year of good history versus six.

That said, I personally don't like Martinez as much this year as the past because he has a poor record in Detroit stadiums.  BUT, you can't argue that he has the ability to give you 3 or 4 fairly solid years, especially since he will transition to 1B and DH more now.  Montero?  We don't know what he WILL give you.  I would roll with Martinez now, and keep an eye out for a good up and coming young catcher that you may be able to stash on your bench for the future.