The primary lesson everyone learned from reading Moneyball is that walks are good. They make pitchers work and get hitters on base, and runs (Hooray runs!) tend to happen when hitters get on base.

A decade later, walks are still good. That much hasn't changed.

What's changed is that they suddenly aren't so common anymore. 

Mike Vorkunov of The Star-Ledger noticed the trend first, writing a couple weeks back that the league walk rate has fallen off dramatically from where it was in 2009 when walks were drawn in 8.9 percent of plate appearances. In 2013, they're being drawn in 7.9 percent of plate appearances, according to FanGraphs.

Vorkunov rightfully made this out to be a big deal, but I actually think he undersold it. That the league walk rate is poised to finish the year below eight percent isn't just remarkable in relation to where things were five years ago. The league walk rate hasn't finished under eight percent since 1968, a year in which pitchers were practically committing crimes against humanity.

Now, I'm a hopeless baseball geek who gets giddy when there's an excuse to go look at numbers. Vorkunov's article was such an excuse, as I wanted to go and see for myself what the decline in walks is all about.

I found out two things. One was that the points Vorkunov brought up in his article are very much valid. The other, however, was that he only scratched the surface. Combined between his points and what else is out there, there's a lot to say about the decline in walks.

So here I go to say a lot about the decline in walks.

The best place to start is with a point Vorkunov made later in his article, one that should dispel the first thought that crept into my head and that might have crept into your head too:

On average, at-bats are as long as they were in 2009. That season, batters saw 3.83 pitches per plate appearance. This season they are seeing 3.84 pitches.

So no, hitters haven't gotten less patient all of a sudden. The decline in walks has nothing to do with them reverting to their Neanderthal-ish tendency to hack at everything in sight.

But what must be noted is that the steadiness of hitter patience in recent years is not a lack of a trend. Compared to what was going on for the better part of the 2000s, it is indeed a trend. 

Consider this line chart, which shows the progression of the league pitches per plate appearance starting in 2000:

There was a gigantic increase in pitches per plate appearance starting in 2006, and that contributed to a league walk rate that rose each year. The 8.9 walk percent in 2009 was the peak.

That there's been a leveling off patience in the last couple seasons highlights a possible pattern. Hitters used to be aggressive. Then they got more patient. Then they stopped getting more patient. That must have been because pitchers responded by getting more aggressive, right?

Exactly, and that leads us to Jumping-Off Point No. 2 from Vorkunov's article:

For pitchers, getting strike 1 has always been critical, an all-but-sure way to avoiding hitter-friendly counts later on. First-pitch strikes and swings on the first pitch of the game now occur in 60 percent of all at-bats, up from 58 percent in 2009.

There's a bit more at work here, but we need some more numbers before we can continue.

With some slightly more precise first-pitch strike percentages from FanGraphs, here's a look at the shift in both first-pitch strikes and first-pitch swings over the last decade or so.

Imagine you're a pitcher. What you saw in that 2006-2009 window was batters suddenly taking a lot more pitches while continuing to build on a budding trend of not hacking at more first pitches. Wouldn't it then make sense to start laying more pitches in there with the count 0-0?

Of course it would, and that's what happened. And while batters have adjusted by swinging at more first pitches than they did in 2009 and 2010, they're still not being as aggressive as they were between 2002 and 2008. They seem to have gotten the gist that they were giving pitchers free strikes, but they haven't gone back to old bad habits.

Pitchers, however, aren't just throwing more strikes on the first pitch. They're throwing more strikes, period.

In 2009, the league strike rate was 62 percent. In 2013, it's 64 percent. That's a huge jump, as we're talking about thousands more strikes being thrown throughout the course of a year.

The tricky part is that this trend can't be chalked up to pitchers attacking the zone more often. They're actually not, as both Baseball Info Solutions and PITCHf/x have the league's Zone% down from where it was in 2009.

However, one thing that's been happening in recent years is that pitchers are getting more calls on the pitches they do throw in the zone.

Jeff Sullivan of FanGraphs has pointed out that umpires have been botching fewer and fewer strike calls ever since the implementation of the PITCHf/x system in 2007. Robot umpires are still needed, but it will do for now that the human umpires are being influenced by fancy-pants technology.

It's not just the pitches in the zone that are going to waste less often. The pitches thrown outside the zone are also going to waste less often, which is a point that Vorkunov brought up:

In 2009, batters swung at 25.1 percent of pitches outside of the strike zone, according to Fangraphs. This season, they are doing so 30.5 percent of the time. That is a significant leap — and a massive leap from 2004 when they swung at just 16.6 percent of pitches outside the zone, according to the site’s figures.

Point being: Pitches that should be balls are becoming strikes. And not just swinging strikes either, as hitters are also making more contact on pitches thrown outside the strike zone.

Contact on pitches outside the strike zone tends to be inferior contact. That makes this a trend that highlights the fact that the league BABIP has fallen from .295 in 2009 to .293 this year. As such, it's fair to conclude that pitches that should be balls are being turned into both strikes and outs.

And no, it's not an accident that pitchers have become so much more successful at getting hitters to expand the strike zone. Such a thing would be bound to happen in an environment where pitchers are throwing fewer fastballs, and that's what baseball's environment is like now.

In 2009, pitchers threw heaters 59.7 percent of the time, according to FanGraphs. That was down from 60.7 percent in 2008, so the trend had already begun. Now the league fastball percentage is at 57.6, meaning there are a lot fewer fastballs being thrown relative to a couple years ago.

And if the PITCHf/x classifications can be trusted, the classic four-seam fastball is going out of style in a hurry. Four-seamers accounted for 53.1 percent of all pitches in 2009. They now account for 35.0 percent of all pitches.

I doubt that the trend is really that pronounced, as PITCHf/x classifications have been known to be finicky. However, it does seem like there are more pitchers throwing two-seamers, sinkers and cutters than there used to be, so the notion that four-seamers are dying out is certainly believable.

With fewer four-seamers and more, well, everything else being thrown, hitters are facing more pitches with movement than they were facing several years ago. Such a trend indeed would lead to a greater tendency to chase.

Let's stop here and add it all up. What we know is that pitchers are being more aggressive on the first pitch, that they're getting more strike calls from umpires in the zone and that they're getting hitters to expand the zone more often, in part because they've started using more weapons that come in handy in doing just that.

In an environment such as this one, what we would see are more pitcher's counts and fewer hitter's counts, right?

Bingo.

I went and checked out the league pitching splits over at Baseball-Reference.com for the 2009 season through the 2013 season. Splits are kept for counts in which the pitcher was ahead, and there have indeed been more of those in the last few years.

What's more, pitchers have also become more successful when getting ahead in the count.

*Meaning the number of "Pitcher Ahead" plate appearances divided by the number of games.

So pitchers are getting ahead of hitters more often, and they're capitalizing on those opportunities by racking up more strikeouts and allowing fewer hits. Just what the baseball gods intended for pitcher's counts.

The same trend appears with two-strike counts.

Even better is the fact that many of the two-strike counts pitchers are getting these days are of the most extreme variety. The 0-2 count percentage in 2009 was 22 percent. It's now 24 percent, a huge increase for a mere five-year time span.

That pitchers are getting ahead more often and getting into two-strike counts more often are trends that would decrease walks all by themselves. Hitters tend to be more defensive in such counts, and defensive hitters are more likely to avoid deep counts.

So it's no surprise that we're not seeing as many deep counts, and there's naturally a double whammy thing going on. In addition to less frequent, three-ball counts have also become less friendly to hitters.

In 2009, any hitter who found himself in a three-ball count stood a fantastic chance of drawing a walk or getting a hit. Now their odds of getting walks or hits in three-ball counts are less than fantastic. Combine that with the climbing infrequency of three-ball counts, and pitchers have a huge advantage relative to the one they used to have.

What's even more significant is the type of three-ball count that's become rare. The amount of 3-0 counts hasn't budged, as it's still five percent and has been five percent for over a decade now. But 3-1 counts occurred nine percent of the time in 2009 and now only occur eight percent of the time. The quintessential hitter's count is being phased out.

What about 3-2? What's happening in the one count where things could go either way?

Take a wild guess.

There's been a spike in 3-2 counts in 2013, but they're still not happening as frequently as they were in 2009, and the success pitchers are enjoying in 3-2 counts reflects the success they're enjoying in all three-ball counts.

The pressure used to be on pitchers when the count went full. Now it's on the hitters.

What it all comes down to is that walks aren't happening as often because today's pitchers just keep finding more and more ways to get the upper hand on today's hitters. They're getting ahead more often because they're going right at hitters with complex arsenals, and they're both putting themselves in fewer walk situations and enjoying more success in walk situations.

If you needed more reasons to believe that today's pitchers are just outstanding, well, there you go.

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