Explaining Analytics: batted balls (or: why grounders are great)

Game No. 162

Credit: Getty Images

Even as tremendous a year as Yu Darvish had in 2013, his batted ball rates indicate the best is yet to come. (Photo by Ronald Martinez/Getty Images)

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by JOSEPH URSERY

WFAA Sports

Posted on February 4, 2014 at 6:54 PM

Updated Tuesday, Feb 4 at 7:59 PM

The best single instant of sports is when bat and ball make contact. There's the crack, and for just one fraction of a second, everything stops. 

 
It all starts right back up as soon as we realize that it's a routine grounder to short, or a liner, or a fly. That's where the poetry stops and the analysis begins. The rate at which a ball comes off a bat as a groundball, or as a line drive, or as a fly ball is important stuff, and it's useful to looking at just about any aspect of baseball that you want.
 
So what are batted ball rates?
 
The ratio to which contact with the ball can be classified as one of the three big categories; groundball (GB%), Line Drive (LD%), and flyball (FB%). There are also infield popups, but those typically don't add up to much, so let's leave them aside for a bit.
 
This is a metric you can use to examine a hitter or a pitcher, with different uses for each. 
 
So how do I use batted ball rates?
 
That depends on whether you're using them for a hitter or a pitcher.
 
For hitters, we normally use them to estimate whether the current results they're posting are legitimate, or the product of swings of fortune over a small sample. For instance, imagine Player A spends the first three weeks of the season with close to a .400 batting average. Even the most hardened sabermetrician would see a .400 BA and think it's pretty cool, because no one's done it since Ted Williams. But he'd need a lot of examination to determine if this player can continue to hit at that rate.
 
Let's assume this player has a career average of 24% line drives, 47% groundballs, and 29% fly balls. During this stretch, those rates are 22%/55%/23%, respectively. Since we're noticing a jump in the player's groundball rates, we can assume that over the larger stretch, that's going to trend back towards his career mean, and we can guess that as that happens, his BABiP (Batting Average on Ball in Play) is going to trend down as well; this means it's likely that this player is not, then, going to continue hitting .400.
 
Likewise, let's say this player hits a whole mess of home runs in the season's first month (let's say, 8- that's a whole mess of homers, to me). We look, and his flyball rate is a little higher than normal. Flyballs turn into home runs more often than any either type of batted ball, so that makes sense. The thing is, this player usually hits a home run on 9% of his fly balls (that is, his HR/FB rate is 9%). We notice he's actually hitting home runs on 8% of fly balls over this magic month, so it's a safer bet that the month might not be much of a fluke, and maybe he's going to continue hitting a whole mess of home runs.
 
With regard to pitchers, the use of batted-ball rates are more important and more powerful. You've all heard the division of fly-ball pitchers versus groundball pitchers. It's a bit of a stretch, because every pitcher would be a groundball pitcher if they really could. Remember above where I said flies turn into homers more than anything else? The home run rate on ground balls is pretty miniscule. Generally, the batter does not want to drive the ball in the ground; getting him to do so is a victory for the pitcher. 
 
But the combination of different velocities, pitch types, pitch shapes, release point, and command that pitchers have lead them to different styles, which lead to different batted ball profiles. Generally, in order of preference for pitchers, we want groundballs (turn into hits pretty often, but those hits are often not more than singles, so it's a decent tradeoff), then fly balls (turn into outs a lot, but also turn into doubles and homers a lot, which are really bad), then line drives (almost always turn into a hit, often for extra bases). In a wonderful, ideal pitcher, you'd see something like 50% groundballs, 35% flys, and 15% liners.

So what do batted ball rates say about the Rangers?
 
Yu Darvish had a weird year last year. In 2012, he allowed 31% flyballs, and home runs on 9% of flyballs. In 2013, he had a 38% flyball rate, and homers on 14.4% of flies. The additional flyball came at the expense of grounders (46.2 % GB rate in 2012, and 41% in 2013).  It's safe to assume he'll see a drop on flyball rates, and a drop in the rate at which flyballs go over fences in 2014 - which is to say there's evidence Yu Darvish will be better in 2014 than he was last year. 
 
Prince Fielder was made available partially because last year did not measure up to the standards he set for himself. In part, that's because he hit 25 home runs, his lowest career full-season total. While his 36% Flyball rate wasn't far off his 39% career average, his 13.5% HR/FB in 2013 was well below his 19% career average. The bet is that Fielder's 2014 will head back up, so that's more reason for optimism in 2014. 
 
An easy way to explain the split between new analtyic types and the classic statistical bunch is whether you look at the surface numbers (RBI, BA - the classical stats) or the numbers behind the numbers (such as batted ball rates).  If you're more familiar and comfortable with those upfront numbers, GB/FB/LD rates are a great metrics to consider.
 
Joseph Ursery tweets about batted ball rate at @TheJoeUrsery. He also tweets about craft beers and his young daughter, so if any of those draws your interest you should follow him on Twitter dot com.

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