Get this: injuries are bad for baseball players and their teams. It is a tough and shocking truth, but I’ll be brave enough to put it out there.

Recovered yet?

I don’t think I need to elaborate on that point, at least not on the obvious dimensions: the lost playing time, the (usually) inferior replacements, and so on. However, something quite different has struck me this year: the way season-ending injuries can make players look better than they should. I call it the “injury halo.”

It may seem like I am setting up a straw man, and perhaps I am. However, I believe we can identify a number tendencies in this direction that would suggest I’m not making something up simply to argue against it. Let me give a few examples of injured players to flesh out the tendency of which I’m thinking. (I had additional examples in mind when putting this post together (my thanks to Mike Axisa and Brad Johnson for their brainstorming help), but I think these should be enough to get the general point across.

The 2012 Royals have been notable for many things, but mostly for two things: a) terrible starting pitching, in some part attributable to b) many pitching injuries. Probably the most frustrating injury for the organization this season was Danny Duffy’s. Duffy, who will not turn 24 until December was leading the team in strikeouts when Tommy John surgery ended his season back in May. His 3.90 ERA and 3.97 FIP may not be earth-shattering these days, but they are above-average numbers for a starting pitcher, Duffy is young, and it is far better than anything else the Royals had in the rotation.

That is, except for Felipe Paulino, a wonderful, practically free pickup by Dayton Moore from back in 2011. Paulino had a 1.67 ERA and 3.26 FIP until going down to injury in June and requiring Tommy John surgery as well. Also like Duffy, the 28 -year-old right-handed starter was strking out more than nine per nine innings. Yes, the injuries are disappointing, the thinking goes, but imagine how much better the Royals would have been if those two guys had stayed healthy! Heck, if they recover and can come back before the break next season, the Royals could have two top-of-rotation starters on their hands!

Sticking with the theme of Tommy John surgery, let’s turn our eyes to Texas. The Rangers have had their share of injuries, too (and obviously, it has killed their playoff aspiration, so let’s give Dayton Moore a break, ya’ll). Of most interest for the purposes of this post is Neftali Feliz, who transitioned back to being the starter he (mostly) was in the minors after two good years in the Rangers’ bullpen. At the time he went down, his ERA was 3.16. A big loss for the Rangers, but their rotation is going to be be good when he gets back sometime in 2013 or (more likely) 2014!

Turning briefly away from the the pitching mounds of the American Heartland, we have Red Sox third baseman Will Middlebrooks, the man who made Kevin Youkilis expendable. Middlebrooks wowed Red Sox Nation with an impressive .288/.325/.509 line before going down for the year with a broken wrist. That is a hard loss in a miserable Red Sox season, but he should be a fixture at third and a stud in the middle of the order for Boston when he comes back for years, right?

Obviously, no one thinks these injuries are a good thing. That would be a straw man too ridiculous for even me. The mindset I am addressing is the one that inadvertently puts an “injury halo” on the pre-injury performances such that a few different things might run through our minds. For example, “man, this team would totally have been three wins better if we’d had that pitcher with the sub-2.00 ERA all year;” or “yeah, it sucks losing that guy to injury, but man, he was awesome before that, this team is going to be unstoppable when he comes back!”

The latter is perhaps a bit over-the-top. Serious fans understand that injuries are not a simple thing to overcome. I do think that in the wake of so many post-Tommy John success stories, we are a bit too blase about coming back from them. But I am not a doctor, so I am not going to get into that. I am addressing the weird effect that season-shortening injuries can sometimes have on the perception of a player’s true talent, both before and after the injury. Let’s go to our examples.

Danny Duffy is a promising young pitcher. A lefty who can throw 95 and strikes out nine per nine innings is a good thing. But what’s lost in the raving about Duffy (and how much it hurt the team to lose him) is that his “domination” (and let’s not go nuts — a 3.90 ERA and 3.97 FIP are good, but hardly dominant) this year lasted six starts and just under 28 innings. While his strikeouts went up from 2011, so did his walks — almost six per nine innings. The smaller the sample is (and this sample is small), the more indicative FIP and xFIP are, and his xFIP this year was 4.79. And while Duffy is young, pitchers do not generally improve the same as hitters — there is not generally an observed mid-to-late-20s peak. Thus, we cannot simply posit an age-based improvement over Duffy’s mostly poor 2011, which provides a much larger sample (105 IP) of poor performance (5.64 ERA, 4.82 FIP, 4.53 xFIP).

If one simply looks at Duffy’s rate stats (well, other than his walk rate) for 2012, they look impressive. It is easier than one might think for people (especially, but not only, fans and hometown writers, who understandably want to be optimistic) to gloss over the sample size issues, especially given the horror that is the 2012 Royals rotation. But there is very little indication that Duffy would have been able to keep up a sub-four ERA all year. Thinking that the Duffy injury cost the Royals two or three wins in 2012 is over the top, as penciling him in as an above-average starter when he gets back (especially given the lost developmental time). It might happen, but the overall statistical evidence suggests that this would be an optimistic projection. That is what the injury halo can do.

This pattern repeats itself with out other examples, too. Duffy’s teammate Paulino barely has a larger sample this season than Duffy: just under 38 innings. Moreover, his peripherals are better (his 3.58 walk rate in 2012 is almost as good as his 3.55 in 2011) and Paulino was actually good in 2011, unlike Duffy. However, while Paulino was an excellent pickup by the Royals, it is not as if he’s in the clear. For one, he gets hurt pretty often. Paulino’s only Major League seson without a Disable List stint was 2011, and even then, he only threw about 140 innings, split between the bullpen and starting. Paulino should be given every chance to start given what he has done, but he can’t be considered a sure bet to be above-average, either, given his past injuries, this injury, and the small sample of his performance overall in the Majors.

The Feliz story is similar: a good ERA as a starter this year, but poor peripherals (4.65 FIP, 4.99 xFIP). Now, I am not one to summarily dimiss non-DIPS stats, but given the extremely small sample in 2012 (a little over 40 innings), FIP and xFIP are more telling. Moreover, his 2012 control problems (4.85 BB/9) already cropped up last year while he was still in the pen (4.33 BB/9). Feliz may simply go back to the bullpen when he returns, I do not know. But his success as a starter seems to be something of another small-sample mirage.

Will Middlebrooks’ situation falls into a different catagory, of course, because he is a hitter. But the same issues are present: 286 plate appearances is not “nothing,” but it is barely just across the line of being “something.” Look, if a player is going to have one tool, power (.221 ISO in the majors this year) is a pretty good one to have. But let’s not go completely nuts — Middlebrooks has good power, but his career isolated power in the minors is less than .180. Moreover, wrist injuries often suppress power even after the player is cleared to come back. So let’s not hand him the next Home Run Derby title just yet.

Middlebrooks is no Kevin Youkilis when it comes to plate discipline. A 24.7 percent strikeout rate is poor, but not necessarily a killer, if it comes with a walk rate over five percent. Yes, like the power numbers, these are in a small sample (although walks and strikeouts stabilize more quickly than other rates), but they are consistent with his Minor League performances.

As Jack Moore has pointed out, Middlebrooks’ power still gives him a chance to be a good hitter. However, we are still working with a small sample from 2012 that leaves plenty of question marks. Based purely on rates, Middlebrooks looks like a potential superstar. Looking at his peripherals, Minor League performances, and yes, our old friend “sample size,” things are not quite so promising, even without considering the lost development time and the effect the injury might have on his power.

So, yes, I suppose much of what I just wrote is just a variation on the classic sabermetric themes of sample size and true talent. However, I think they are worth repeating. Many fans and columnists have succumbed to the temptation to look at injured players and see their loss as more devastating than they should be (because that player would not have regressed to the mean, of course!), or sees their return as a likely boost. The injury halo can be tempting for all of us. That does not mean we have to give in to it.