The Cardinals' depth on the position player side is in kind of a weird spot going into 2016. Let's take the outfield and first base position, as a group of four positions. Those four positions can be covered pretty well by 6 players; Matt Holliday, Randal Grichuk, Stephen Piscotty, Matt Adams, Brandon Moss, and Tommy Pham. Due to the positional versatility of the those six players, the only combination of four that couldn't fill in those four positions would be the only one that doesn't include Tommy Pham and Randal Grichuk, as those two are the only center-fielders of the bunch.
So six players for four positions sounds like reasonable depth, but there are some problems. For one, you don't really want to see Matt Adams or Brandon Moss see significant time against lefties. That right there means all six have to be healthy for Adams and Moss to both sit when a lefty is on the mound (or the team would have to call upon Triple-A right handed hitter and Corner outfielder Anthony Garcia).
The other main problem is the aforementioned two outfielders are two of the toughest players to keep on the field. Alex covered Tommy Pham's injury problems in the minors and Grichuk has his own storied minor league injury history: drafted in 2009 and tore a ligament and broke a wrist in the 2010 season. His 2011 season started late after fouling a ball off his knee, fracturing his kneecap.
Charlie Tilson would be the presumed third-string center-fielder at this point. While he has taken 739 PA at the Double-A level he's yet to play at Triple-A. He's very likely to start the year at Triple-A, but he seems like a good bet to get called up at some point when inevitable injuries occur. He's coming off a 107 wRC+ at AA last year, but minor league wRC+ isn't park adjusted and Springfield is great for left-handed hitters (just ask Daniel Descalso, who posted a 151 wRC+ there in 2009). However, The Red Baron liked Tilson's defense and base-running, so even if he's a below average hitter in the majors he could still provide above-replacement value, and that's nice to have out of a 3rd-string center-fielder.
Anthony Garcia is in a similar position, though he bats from the other side of the plate and would likely be called upon if the Cardinals are looking more for help in the corners. He enjoyed the Springfield hitter's haven as well to a 149 wRC+, but also hit at an above average level in a 64 PA cup of coffee at Triple-A to end the year. The Red Baron loves his ability to produce offensively, so its not exactly a nightmare situation if he ends up in a part-time role or playing everyday for a short stretch of time.
How likely is it we'll see Tilson or Garcia? A couple of weeks ago I looked at Jeff Zimmerman's great work on projecting injury risk for Starting Pitchers. This year he started calculating a "days missed" projection for position players, using a calculation Robert Arthur came up with two years ago. There are limitations to this calculation, namely that it only considers prior injuries and to much less degree, age, and it treats all injuries similarly. However, it at least gives us some more information. We're never going to be able to pinpoint something like that too precisely. Arthur and Zimmerman's research both agree that the number one predictor of future injury is past injury. And for a team that suffered too many injuries to remember last year, that's not good news for the Birds on the Bat.
Here is Zimmerman's calculation for the Cardinal's position player risk, using Arthur's formula:
Notably, Zimmerman did not use any Minor League injury data, but Grichuk at least avoided the injury bug in 2013 and 2014 anyway. The same cannot be said of Tommy Pham, who accumulated less than 700 combined PA between 2013 and 2014. Zimmerman did not publish a projection for Brayan Pena. Greg Garcia is likely to round out the bench (though Aledmys Diaz will be competing for that job as well) but he and Diaz's lack of a major league track record and projected bench role make their injury projection somewhat unnecessary.
With that in mind, It's unsurprising that Matt Adams leads the team in projected days missed; he missed more time than anyone listed here in 2015 and is the only one on the Major League DL all three years (though Molina would have tied him for that distinction had he not gotten injured after rosters expanded in September 2015, making a DL move unnecessary).
So, the outfield and first base situation has some depth, but it also has a lot of injury risk. The three players with the highest injury risk on the team are all part of that configuration. Here we see the relevance of a recent injury over just two or three years ago, as Holliday gets a high risk ranking despite being very durable throughout his long career. And of the other three, no one has an unblemished record. Grichuk was injury prone in his early minor league career, Moss escaped the DL by having off-season surgery, and Piscotty escaped the DL by managing to get hurt in September with extended rosters. Of those three, Piscotty probably should be considered the least injury prone, as his sickening collision with Peter Bourjos was truly a freak occurrence.
At the skilled infield positions, things look likely to be more stable. Peralta and Carpenter have both avoided the DL each of the last three years, though Carpenter's issues of extreme fatigue last year may have deserved a DL trip had the Cardinals had a half way viable back-up third basemen last year. Peralta is about as durable as a 33 year old (soon to be 34) bigger-than-average shortstop can be. Since becoming a full-time player in 2005, his lowest PA total was 448 in 2013, due not to an injury but his PED suspension. His lowest after that was 570, all the way back in that first full time season in 2005.
Wong had his shoulder issue in 2014, but other than that has missed the DL. He had high PA totals in the minors, with over 200 PA in his draft year, over 600 the following year, and missed the 600 PA threshold in 2013 only because he was a part-time player following his promotion to the majors. So one recent issue for Wong.
If something did happen to Wong or Carpenter, it looks like Jed Gyorko will get the first chance at the extra playing time. Gyorko dealt with Plantar Fasciitis in 2014 and a groin injury in 2013, but managed to stay healthy throughout 2015. That leads to a projected 24 days missed projection, but unless Marp or Wong get hurt, Gyorko won't be an everyday player, leading to less chances to get hurt.
Molina received the same 24 day missed projection, and he's the last starter to discuss. There is the distinct risk that Molina doesn't start opening day due to undergoing a second thumb surgery this off-season after the first one "didn't take". Even if he does, it may be more indicative of the Cardinals rushing Molina back than him truly being healthy, similar to what happened last year with Holliday and Jon Jay. Even if he does come back 100% healthy though, he still carries a decent injury risk. Pena is a competent fill-in in the short term but there's a reason he's been a career back-up rather than a starter. The options past Pena are very thin unless Mike Ohlman breaks out at Triple-A this year.
And that's why I would say the Cardinals' depth is kind of weird. They certainly have depth, in the sense that they have some players that could start on some other teams sitting on the bench. Tommy Pham probably meets that standard as well as one other outfielder or first basemen, probably Matt Adams or Brandon Moss. Jedd Gyorko, if he were a free agent this winter probably could have found a job promising more playing time than backing up Matt Carpenter and Kolten Wong in St. Louis. Pena is a career back-up catcher, but one of the relatively better ones.
However, the Cardinals might have to test that depth more than other teams, due to the injury concerns presented here. Peralta is about as close to an everyday player as you can get in this era, and Piscotty's only blemish thus far is an injury that probably offers no real prediction value of future injury. Other than that, there's a reason to be concerned about every other position player that could receive a lot of plate appearances in 2016.