Unlike the catching position, most all organizations have a few prospects who have a shot at making the big leagues while standing near the first base bag every half inning. Mostly, they'll make it due to what they do standing in the batter's box during the other half inning. The position has long been one at which teams hide a great bat who can't play anywhere else on the field, and there's usually a surplus of those running around the freely available talent circles of the major and minor leagues.
That said: this crop of Cardinals might be one of the worst I've seen in an organization in terms of the possibility of future big league production. It's a real sore spot for the Cardinals in the minors, and one reason why the team probably isn't trading Allen Craig or Matt Adams any time soon -- they provide the only depth at the position that the team really has at this point.
Jonathan Rodriguez is the real gem of this bunch. He graded out as a C prospect coming into the season, but if he continues to hit well at Springfield he'll likely push himself up into the B-/B grade by the end of the year. That's saying a lot since B grade first base prospects would generally be an elite bat just about anywhere else on the diamond. So far, though, Rodriguez has shown plenty of reasons to think that he might be one of those guys: .315/.398/.598 in the Texas League with a .283 ISO and a 173 wRC+ is the definition of elite, and the sample is big enough, and doesn't differ a ton from his minor league track track record, that there's some real projection in that bat -- the .373 BABIP not withstanding.
Xavier Scruggs came off a solid 3TO season at AA Springfield a year ago, despite being a bit old for the league, but has really struggled this season in AAA where his inability to make consistent contact has really put a huge damper on his power numbers with Memphis. Scruggs' ISO has been consistently in the mid-.200's for the last four seasons, but is sitting at a paltry .122 this season, even while he's striking out less (although, notably, still doing so nearly 27% of the time) and sporting a good average on balls in play (.313). Hopefully he's able to recover his power stroke over the next few months, but Scruggs turns 27 soon and will be a minor league free agent at the end of season. With Rodriguez performing so well at AA it would seem like Scruggs' days in the organization are likely numbered.
Until, of course, you look at the rest of the minors. A few words come to mind: Ugh, blechhh, holy moly that's a pittance of talent. For a position where most teams hide a bat, the Cardinals seem to have hidden the bats from their own first baseman, forcing them to hit with broomsticks and toothpicks instead. That's really about the only way to describe how bad most of these guys have been. The worst part is that none are young for their league and most are college bats that should already be polished enough to hit in the low minors.
David Washington came off a pair of solid seasons in short season ball and was promoted straight to Palm Beach after a solid spring, but he's done nothing but struggle his first six weeks at High A. He's had a bit of bad luck (.210 BABIP) so far this season but he's not yet been able to break out of it either. Washington should probably take a step back to the Midwest League to see if he can find his stroke again with Peoria
It's not like Jake Stone or any of the short season hitters are going to be holding up that demotion either. Justin Ringo is a possibility for later in the season I suppose -- he hit .300/.387/.445 in 231 PA's with Johnson City last season after being selected in the 28th round of the draft out of Stanford. Ringo is the prototypical "Stanford hitter" as well, making lots of contact with gap power. In a lot of other organizations he'd probably get buried by a few raw power guys, but might end up starting 80+ games at Peoria by the end of the year in this one.
I wouldn't necessarily say that this is a position of need for the Cardinals, as first base is generally not a position you draft for. Rather, you draft an elite bat that you think can play somewhere else on the diamond and then move him to first base when he proves that he can't. The Cardinals organization has had a tough time finding elite power hitting prospects as of late, and that's partially the reason why there's such a glut of first baseman currently in the system. Perhaps the team should move some players to first base rather than outfield for a change.