(Almost) all of the newly acquired prospects
Okay, so this isn't going to be about the specific third prospect the Cardinals shouldn't call up. It's actually about the rather large number of new prospects St. Louis traded for leading up to the August 1 trade deadline. Given where the big league team is headed and the status of their new acquisitions. promoting just about any of them doesn't make much sense.
Among the current big leaguers, Dakota Hudson and Matthew Liberatore should be given opportunities to show what they can do in the rotation. The team also should give strong consideration to including Zack Thompson in the starting mix, even if that means going to a six-man rotation or bumping Cardinals legend Adam Wainwright to the bullpen amid his painful-to-watch final season.
There simply aren't rotation spots available this year for Drew Rom, and Sem Robberse, with the latter not yet on the 40-man roster. Meanwhile, Tekoah Roby is still recovering from a shoulder injury, so there's a very different focus for him than considering a big-league debut.
On the position player side, Cesar Prieto has played third base, second base, and a little shortstop in the minors, positions at which the Cardinals already have good depth. Thomas Saggese has a similar defensive profile to Prieto, and he's currently at Double-A Springfield, so the odds are even slimmer of him making an appearance at Busch Stadium this year. Given St. Louis' roster construction, it wouldn't be surprising to see either or both of these players dealt in an offseason move to acquire even more pitching.
About the only reasonable call-ups among the newly acquired talent would be relievers Adam Kloffenstien, currently pitching for Memphis, or - as a real stretch - Matt Svanson, who is toiling for Springfield. Relievers are fickle, so seeing what either of them could do against major league hitters this September might give the Cardinals a slightly better sense of their ability to contribute to the bullpen next season.
Sometimes teams will bring their new acquisitions to the majors to give fans a demonstration of what all the trade deadline deals were about, to let them see those transactions are paying dividends right away, even if immediate impact is not the real intention of those moves. For St. Louis, most of their fans know better, that what's most important is figuring out who on the current roster should stick around while using the minor leagues to continue refining the skills of their youngsters in full-time roles so they'll be ready to help the big league squad when their number is called.