The only argument one can make against the Contreras move being great is that hes 34, 35 next year and if the team doesnt start winning soon, this year could be shot. At which point he could become a trade chip at hte deadline this year, if we fall too far out of it ,but I dont think they would do that.
If the team make the playoffs this year, hes a great add, or at least as great of an acquisition as getting a 1-2 yr contract attached to an old player can be.