Per various folks in the Twittersphere, including Rangers p.r. guy John Blake, Yoshinori Tateyama has been added to the Rangers' ALCS roster, with Matt Treanor being dropped from the roster.
I'm not really doing backflips over this move...a four man bench, with just the one backup catcher, reduces the tactical flexibility that the Rangers have late in game. That said, with Detroit starting only righthanded pitchers in the ALCS, Mitch Moreland is going to play first base every day, which means that you won't have both Yorvit Torrealba and Mike Napoli in the lineup at the same time.
Still, it seems unlikely that you are really going to need eight relievers in this series. Tateyama gives the Rangers a righty specialist you can match up against a couple of righthanders late in games, but he can't be left in to face lefties, and he struggled down the stretch, so I question how comfortable Washington is going to be using him in a tight situation anyway.