Raising the strike zone could have unintended consequences

Jayson Stark reported on Friday that MLB's competition committee has agreed to a change in the strike zone for 2017, pending approval by the rules committee. Jayson wrote:

The committee agreed on a motion to effectively raise the lower part of the strike zone to the top of the hitter's knees, sources said. The current rules stipulate that the zone begins at "the hollow beneath the kneecap," but the change is a reaction to a trend by umpires to call strikes on an increasing number of pitches below the knees. ...

Sources said the changes would also be presented to the MLB Players Association as part of negotiations for a new labor agreement. However, the playing rules committee isn't required to have the union sign off on the changes, which could take effect next season whether or not the union agrees to them.

Jayson's report said the proposed change is tied to concerns about "pace of action," as commissioner Rob Manfred likes to phrase it, more than declining levels of offense, with the intended goal of a smaller strike zone leading to fewer strikeouts and more balls in play. It's important to note, however, that while strikeout rates have continued to rise upward, hitters seem to have regained some of the balance of power. Offense declined to 4.07 runs per team per game in 2013, the lowest total since 1981, but climbed to 4.25 in 2015 and is at 4.28 this season.

As Joe Sheehan wrote about the proposal:

The idea with the rules change is that pitchers will have to work a little higher. This change should raise offensive levels a little bit, but its real goal is to raise contact rates through a higher percentage of hittable pitches. It's not certain that it will happen that way, because messing with the strike zone is a risk that invites unintended consequences. It is, however, a reasonable approach to the problem.

I'd suggest: Be careful when you mess with the strike zone. When the rulebook definition of the strike zone was changed in 1963, a new era of pitching dominance was ushered in, culminating in the Year of the Pitcher in 1968, which led to another redefinition of the strike zone. The rise in offense may not be small with a raised zone, but huge. Walk rates could climb significantly, leading to more pitches and more walks. More balls in play plus more walks would lead to more runs, which would mean even longer games, which isn't the same thing as "pace of action" but is obviously a related issue.

But how much would offense increase if the bottom of the zone is raised an inch or two? Somebody smarter can do a more precise analysis, although it's sort of impossible to know, because the ramifications of how pitchers and batters would adjust are unknown. We do know that pitchers benefit from a lower strike zone. When we divide the strike zone into three areas of vertical location, here's how batters have fared in 2016 on plate appearances ending with pitches in those locations (not all pitches):

Upper third: .234/.387/.399

Middle third: .308/.330/.525

Bottom third: .246/.323/.388

As you would expect, hitters cream pitches in the middle of the zone, but while they hit for a higher average on pitches in the bottom third compared to the upper third, they post a higher OBP (more walks) and hit for more power on pitches in the upper third.

Pitchers today often put batters away with breaking balls below the knees or off the plate. I don't have the data to isolate with precision how batters fare on pitches at the top of the knees versus the bottom, but I do have numbers to compare "competitive" pitches to "noncompetitive" (pitches more than 18 inches from the center of the strike zone). If we take results in the lower vertical third of the zone (or below) and break them out into those categories, here's what we get:

Competitive: .269/.306/.432

Noncompetitive: .108/.398/.133

Not surprisingly, when batters swing at pitches well out of the zone, they don't produce much; when they don't swing, they draw walks. But this is where batters will be helped: If a hitter knows he can lay off a pitch he currently has trouble doing damage against, he can become even more selective and force the pitcher to come up in the zone.

I went back to 2009, which is essentially the last season of bigger offense (4.61 runs per game) before the strike zone started getting lower. Here are the results on competitive pitches in the lower third of the zone compared to 2016:

2009: .310/.333/.509, 12.0 percent K rate

2016: .269/.306/.432, 20.1 percent K rate

Of course, maybe pitchers are just better now (and throwing harder), so the results may not flip right back to 2009 levels. But it provides an idea of what might happen. What does this mean in terms of scoring runs? As I was writing this piece, I found this study by Jon Roegele from 2015 at The Hardball Times site. There are a lot of data points in there, but he concludes:

If the bottom of the strike zone reverted to its 2009 height, this analysis estimates about 1,000 additional runs would be scored over the course of the season. If we augment the 2014 run total by this difference, it brings the runs scored per team per game up from 4.07 to 4.27. Once again, this closely matches the run environment experienced in the league in 2012.

Factor in that offense has already increased from 2014 levels, and maybe we're looking at 4.5 runs per game -- or something close to 2009 levels of offense. It's worth noting that those levels were still below the peak levels of the steroid era (5.14 in 2000), so I don't think we'd suddenly see a surge of 50- and 60-home run hitters.

Whether a higher zone would increase the pace of action, I don't know, but it would certainly create more offense.