Juan Yepez as a trade piece at this deadline
If Yepez does not have a role on this roster in its current state, does that make him trade bait for the Cardinals in their pursuit to upgrade their pitching? Short answer, yes. The long answer, it depends on what kind of package they need to put together.
I would imagine clubs that are looking to rebuild or retool their lineup would love the idea of Yepez in their order. Most teams will value Yepez a bit less than other trade pieces though for the same reasons the Cardinals do - the lack of a true defensive position. But his bat plays, and there's always a need for offense around the league, especially when the bat has five years of team control.
Here's where it gets a bit complicated though. Sure, Yepez is probably one of the Cardinals' first options to be traded, but if they enter into negotiations for a front-line starter, they may need to create a different kind of package. Maybe the club really likes guys like Dylan Carlson, Tyler O'Neill, or Alec Burleson, and a few of those guys end up in a trade instead. Now Yepez goes from the odd man out in St. Louis to a valuable contributor.
In all likelihood though, I would expect Yepez to be on a different team after the trade deadline if the Cardinals seriously pursue starting pitching. Any package for pitching will require multiple assets, and I can see Yepez being the second or third piece in a larger trade for an impact starter. Yepez will likely go on to be a valuable bat in this league and put up numbers for a team that plays him every day, I just don't see that being with St. Louis.