Anyone that has watched baseball recently knows that runs have been at a premium in the past ten years. Major League Baseball games have shifted from slugfests in the 1990’s to an art where many teams are comfortable with scoring as little as three runs. This undoubtedly has something to do with the haze of steroids being phased out of the game, but that may not explain everything. If steroids were the only reason for this shift, runs would presumably stop dropping at a consistent rate. Pegging down the culprit for this minimizing run production is not easy and hard to effectively attribute to a few sets of data. However, recent trends show interesting relationships between strikeouts, and more importantly the components of strikeouts, that may be influencing this run scoring environment. .
The idea that strikeouts have a significant impact on run scoring is usually an idea thrown around by baseball traditionalists and scoffed at by more data- based analysts. The statistical thinkers may be quick to point out that there
is generally no correlation between strikeouts and run scoring. However, the relationship shown in the graph to the left indicates that this association may be worth digging deeper into. While correlation does not imply causation, it can indicate relationships worthy of further research. This immediately brings up further questions that need to be tended to. Could there be a developing relationship between strikeouts and run scoring in this post-steroid era? Could strikeouts possibly matter more, in terms of run production, than any other out? Could strikeouts, as a whole, not actually be the true culprit of the problem? An investigation into the third question may be able to lead us in the right direction.
It is generally still understood that putting the ball in play is better than striking out, but striking out itself does not sap the life out of an offense. I briefly touched upon this concept in my first article, where I made an argument based on correlational data. This data showed that over the last ten years, there was not strong evidence to support run scoring relating to strikeout totals. In this era, players with high strikeout totals can still be offensive stalwarts. Not many people even batted an eye when Chris Davis struck out 208 times this year, or maybe didn’t have time to between his home runs. With this concept seemingly understood, we can start to look at WHY people strike out and try and find some semblance of a connection between these factors and run output.
This graph to the left shows swing percentages in major league baseball since the inception of this data in 2002 (provided by FanGraphs). “Z-Swing%” represents the percentage of balls in the strike zone that players swing at. “O-Swing%
” represents the percentage of balls out of the strike zone that players swing at. “Swing% is the aggregate of the two. This graph seems to show that while players overall are swinging at relatively the same amount of pitches, they are swinging at less strikes and more balls. In other terms, batters are swinging at less good pitches and more bad pitches. This, alone, does not fare well for run output, and is assuredly going to impact the overall strikeout rate in the MLB. In fact, there is almost a direct correlation between “O-Swing%” and “K%”, leading me to believe that it is one of the driving factors of the rise in whiffs.
So what does this relationship have to do with run scoring? Instead of looking at strikeouts and run scoring as independent and coincidental, common threads can be found to tie all of these factors together. This graph depicts a 
potentially significant connection between the two. This shows contact percentages over time with “Z” and “O” still representing “in strike zone” and “out of strike zone”, respectively. This shows that while players are making relatively the same overall contact and the same contact with pitches in the strike zone, they are making way more contact with balls out of the strike zone. Fundamentally, players are going to make weaker contact with balls out of the strike zone. Some players, such as Pablo Sandoval, can provide a rare exception to this rule, but most hitters making contact with pitches out of the strike zone should not be expected to be spraying line drives all over the field. In fact, Soft Contact%, which measures how hard a player makes contact with a pitch, has been similarly down over the last ten years. This concept should make sense, as players are swinging at less pitches in the strike zone which they can drive and swinging at, (and making contact with), more pitches out of the zone which they cannot. This inability to drive the ball would seemingly make scoring runs a burdensome task, and both factors going into this have increased where run scoring has decreased. Perhaps this connection is behind the recent run-scoring deterioration.
This apparent dynamic seems to point to a common thread between strikeouts and run scoring; understanding of the strike zone. Players who swing at balls out of the strike zone are obviously going to strike out more, and if they are making contact with these pitches, the balls they put in play are going to be significantly less impactful. Strike zone discipline, or lack thereof, seems to be affecting both strikeouts and run scoring. The fact that there seems to be less and less players with effective strike zone disciplines is certainly interesting. Finding the cause of this trend is the hard part. Are players simply getting worse, or caring less, about understanding the strike zone? These days a 100-strikeout season is almost expected out of a player, and double that is no longer considered a crippling total. Are teams putting players in tougher positions to be disciplined? Some teams stress that players get deep into counts, or even dictate when they can swing, therefore limiting their ability to hunt strikes to put into play. Are pitchers forcing players to be reckless? Perhaps this is truly a consequence of flamethrowing pitchers and players just have less time to react and decide if a pitch will be in the strike zone. There is no concrete conclusion that I can derive from this, but instead this data provides a relationship to pay attention too. Perhaps teams will begin to further emphasize plate discipline in young players, as these relatioships seems to show that it not only influences just how often a player walks, as previously thought, but how often they can find pitches to effectively put into play.
