A growing trend over the last several seasons has been the use of defensive shifts. Think about it: you can probably imagine at least one player, right off the top of your head, who routinely gets "shifted." Joe Maddon of the Rays often gets credited with moving his infield around, but it's catching on throughout baseball and almost nobody plays David Ortiz straight up anymore. At this point, it's safe to say that the defensive shift is here to stay.

The reason behind this, of course, is that batted balls for many hitters are fairly predictable. In fact, we know that the majority of hitters tend to pull the ball on the ground and go to the opposite field when they hit flies (like Troy Tulowitzki, for example). This is a generalization, but it holds up relatively well across the baseball spectrum. Knowing this, it was only natural that teams would begin moving their fielders to accommodate for these tendencies, especially the hitters who exhibit extreme ones. Take for instance Carlos Pena. We can easily see where he hit the majority of his balls from 2012 to 2013:

It would make perfect sense to move your fielders to better position them to handle this type of hitter. He's an extreme case, but there are certainly other hitters like him out there.

In fact, the original hitter to get shifted very well may have been Ted Williams, so while this idea has caught on with extreme pull hitters at the plate in the last couple of years, it's not necessarily original. The frequency of them, however, has clearly increased, perhaps 100-fold. As Chris Cwik pointed out back in December, these shifts are incredibly hard to track because we don't have reliable data on them. This may change with the new MLBAM system to be unveiled this year (in three parks), but for now, we don't have a lot to go on.

But I want to steer this topic in another direction. While at the SABR conference in Phoenix two weeks ago, I heard a very unique concept espoused by MLB.com writer Barry Bloom. He asked aloud if the shift is ruining baseball and if there should be a mandated balance for infielders, perhaps limiting the area where they can be lined up before each pitch. I've never heard of this viewpoint before and while I think it's a little presumptuous to say that Bloom fully believes this, he was clearly comfortable throwing it out there in the open to a room full of bright baseball minds (and me).

Still, I was kind of dumbfounded that the notion of the shift "ruining baseball" was something that anyone could think. It surely puts certain players at a disadvantage and these are often the power hitters that the game has loved so much over the years. But these hitters have their flaws, most notably a bunch of ground outs to the same area on the diamond. The defense has every right to move around to the positions that serve them best. No one's going to be angry when the infield moves in when Billy Hamilton's at the plate, so what's the big deal with the shifts?

Well, the deal is that these shifts are rendering certain types of players less valuable. If the shift is killing pull-hitting players, then they should see their value decrease when compared to hitters that can spray the ball all over the place. Predictability is usually bad in sports, and the types of players who get shifted are the most predictable sort of players. So maybe the issue is the way that some of us value players, not the shift itself.

If the shift is really transforming baseball, as the questions by Bloom (and likely others) alluded to, by rendering pull-heavy hitters less valuable, we would want to know just who these hitters are. To identify them, I create a simple "balance factor" to judge how frequently these hitters pull the ball as opposed to going up the middle and to the opposite field. I used FanGraphs' batted ball data for the location of balls put in play and calculated the "balance factor" with the following equation:

(((Center Rate + Opposite Field Rate) ÷ 2) - Pull Rate) × 100

Positive outcomes show a propensity for going the other way and up the middle, while negative rates show a propensity to pull the ball. Scores of zero show that the hitter has an equal chance to pull the ball as he does to go the other way and up the middle. I only used qualified hitters in this study, and we'll talk more about that in a minute. For now, take a look at the 25 most pull-heavy qualified hitters from 2013 as determined by the "balance factor":

The players above hit the ball to the pull side at a disproportionate rate. Their balls in play to the pull side heavily outweigh their balls in play to center and the opposite field. What's perhaps most remarkable is that the players at the farthest extreme pretty heavily outweigh the players with the (relatively) more balanced approach. Will Venable has been known for making his pull-heavy approach work for him, but Nate McLouth shows up as relatively balanced in comparison. There simply aren't a lot of wildly extreme pull hitters in this sample.

This, of course, gets back to the issue of choosing only qualified hitters. Several extreme pull hitters are used primarily as platoon players given that they tend to struggle with hitting arm-side pitching and are looking to pull the majority of pitches thrown at them. The tendencies of these players have already limited their usefulness as they're highly predictable. It's also worth noting that several of these players are older, DH-types who are using the one skill they have left (power) to hang around. The lack of balance to their game turns them into one-dimensional players and many of these guys are easy to shift (Travis Hafner, Luke Scott and others come to mind).

But which players are hardest to shift, or better yet, are the most balanced hitters? Again, looking at qualified batters for 2013, here are the 25 most balanced hitters according to the "balance factor" I created above:

Again, note that a positive value shows a tendency to go up the middle or to the opposite field while a negative value shows a tendency to pull the ball. The perfect balance, according to this metric, would be a score of 0.00, showing an equal balance between pulling the ball and going up the middle and to the opposite field. Three hitters, Jon Jay, Ryan Zimmerman and Eric Young, hit this mark. While they show some variance in where their batted balls end up, properly shifting these players would be nearly impossible as they exhibit near-perfect balance. While Eric Young is a switch-hitter, it should be noted that the vast majority of the guys on this list hit from only one side of the dish, meaning that this balance isn't simply a result of switch-hitting. Initially I had considered throwing out switch hitters, but they make up such a small proportion of the sample that I decided to include them if for nothing more than context.

So getting back to the original question posed by Bloom, is the shift ruining baseball? While the shift helps to weed out some pull hitters, primarily aging ones or ones that simply aren't that good at baseball, I can't see the argument for it ruining the sport. Despite names like Mike Moustakas and Dan Uggla on the pull list, there are also names like Andrew McCutchen, Ian Kinsler, Shane Victorino and the Blue Jays' Terrible Tandem of Jose Bautista and Edwin Encarnacion. Meanwhile, the list of balanced hitters is equally as underwhelming (Adeiny Hechavarria) and encouraging (Joe Votto, Paul Goldschmidt) at the same time. If the shift were truly ruining baseball, I'd expect to find more variance between the two extremes, but alas, they are relatively similar as even the average wRC+ is less than 2% different when comparing the groups, so both types can be effective.

It should be stated that while we can't tell exactly which players have been shifted the most, the list of pull hitters above would be a great place to start. If these players were being shifted right out of baseball, I think we would know it. If anything, the shift is simply causing fringe-y, one-dimensional players to either be squeezed out of or never allowed into the game. This doesn't sound like something we should be concerned about as ruining our sport, but is rather another sign that our sport is growing smarter every day.

. . .

All statistics courtesy of FanGraphs

Jeff Wiser is an editor and featured writer at Beyond the Box Score and co-author of Inside the 'Zona, an analytical look at the Arizona Diamondbacks. You can follow him on Twitter @OutfieldGrass24.