It could be more the improvement of other teams (Pirates/Cubs), but it sure feels like to me that STL has not been keeping up since the WS loss to Boston. Yes they had the best record in the majors last year during the regular season, but they really struggled in the post season. Many factors have been at play, one of which has been injuries, as you said. Personally, I haven't felt like the Cardinals were an elite team for a few years. They have great stretches, but seem to falter when they play good teams. That's just my opinion, but is backed up with their record against winning teams this year (admittedly a small-ish sample size) Ultimately, i feel like they are slipping and don't want to see them fall behind the likes of CHI and PIT for several years. I have a tremendous amount of faith in Mozeliak to get the right team together to win.
Regarding Peralta: offense is not their problem. They are one of, if not the, best scoring offense in the NL. Pitching and defense have been the problem, obviously. There's a lot of season left and I believe the staff will improve (though I have serious concerns about Wacha). Hopefully Reyes can come up and set the world on fire, but that remains to be seen.
Pardon me sounding doom and gloom. I do think it will be tough for any team to catch the Cubs in the Central, but everything changes come October. Hopefully the Cardinals get to participate. Here's to hoping the pitching improves and the offense continues.