The first question to address is whether this is largely on the hitters, largely on the pitchers, or a mix of both. Since 2005, the average K/9 rate has increased from 6.3 per nine innings to 7.68 per nine innings. In this same time frame, the league batting average has declined from an average of .264 to a .251 average thus far in 2013. If this number holds, it will be the lowest league batting average in 41 years (the league-wide average in 1972 was .244).
While the league-average walk rate has returned to the same rate it was in 2005 (3.12 walks per game), the strikeout rate has noticeably increased. On an average night in the 2013 season, a nine-man lineup will strike out close to eight times. While there is some discrepancy amongst teams in terms of strikeout rates and walk rates, there are currently seven (!) clubs with team strikeout rates above 22% (the Astros, Red Sox, Cubs, Pirates, Indians, Brewers, and Braves). The Houston Astros, in their inaugural American League season, have an astounding 27% team strikeout rate and are on pace to obliterate the K% record by a team, set by the 2010 Diamondbacks (24.7%). This reinforces the notion that it is a league-wide issue, and not a phenomenon relegated merely to the game's have-nots. From the bottom of the payroll hierarchy all the way towards the top, franchises are engulfed by a tidal wave of strikeouts.
A multitude of reasons have been postulated as to the rise in strikeouts, from a widened strike zone, to a narrower strike zone; from more power arms in the game, to the current popularity of "pitches per at-bat," to a continued increase in called strikes by umpires over the past two decades, and so forth. While we are clearly seeing a spike in what could be termed "umpire activism" (when a batter does not swing at such a pitch, the likelihood that an umpire will call that pitch a strike is significantly higher than it was even five years ago), this cannot be the sole answer for such a curious trend.
We are doubtlessly witnessing the era of the Three True Outcomes on an increasingly-widened scale. Fewer and fewer hitters are playing small-ball, while an exponentially greater number of players look to change the game with one swing. There are still a fair share of agile slap-hitters sprinkled around the league, but for the most parts, teams are more willing to give an opportunity to a batter who profiles more like Russell Branyan than a batter who profiles similar to a Juan Pierre.
Still, the strikeout rate is an anomaly, even when taking the Three True Outcomes into consideration. The league-average home run rate has stayed about the same since 2005, and the league-average walk rate has seen a minor decrease in the past decade. In other words, the only area which has steadily risen for batters is the strikeout rate.
While there may be some credence to the notion that there are more power pitchers in the game, there is also the fact that pitchers are throwing fastballs at a greater velocity than ever before, but also at a lower frequency than in previous years. Pitchers appear to be relying more on curveballs and cutters (and less on fastballs) to keep hitters off-balance at the plate.
So, what we have is a strike zone more likely to result in called strikes, pitchers armed (no pun intended) with a wider array of pitches, and players taking an increasingly stoic tact to the plate all contributing to the rise of the strikeout rate in the game today. Additionally, the increased fracturing of the game into multiple pitching assignments (i.e., the starter gets the first four to seven innings, with relief pitchers reserved for the 7th, 8th, and 9th innings) means that at almost any point in a game, a batter is facing a "live" arm, a pitcher that is throwing at full capacity, rather than a beleaguered starter whose arm is taxed after throwing hard for several innings.
Some of this, however, must rest upon a shift in philosophy and approach to hitting since the 1990s. It is too wide-spread to be solely due to tangible shifts in on-field play; something intellectual in nature has to have also occurred or been altered to account for all of this. In the wake of an era fueled by moonshot home runs, we now have a generation of players who grew up watching and mimicking that style of play. This has been coupled with an increase in called strikes, but this may be related to batters appearing to take a more patient approach to the plate. This shift in philosophy would correlate to the increase in called strikes by umpires, as players are becoming less apt to swing at pitches a little out of the zone. With a batter that is more "lax" (for lack of a better term) at the dish and an umpire that is more aggressive in calling pitches than previous generations of umps, we have a scenario in which pitchers work their way into more favorable counts a good portion of the time. This (obviously) also means that hitters find themselves in pitcher's counts more often, dealing with a lot of 0-2, 1-2, and 2-2 counts, which in turn reinforces an increase in strikeouts (whether swinging or called) due to the fact that they have painted themselves into a corner in such a plate appearance.
Now, all of this only addresses league averages amongst teams and players. The outliers of this group, the players who have an unusually-high predilection towards strikeouts of any variety, are what make this phenomenon particularly intriguing. Up until quite recently, hitters with supreme power but high rates of strikeouts and low-to-moderate walk rates were either passed up on time and time again (exemplified by Jack Cust), or flamed out very quickly and found themselves playing against lesser competition (Wily Mo Peña, Wladimir Balentien). Only in the past few years have hitters with such a profile become major-league staples. Players such as Pedro Alvarez of the Pirates, Chris Carter of the
It would appear that an acceptable strikeout rate for a hitter is now as high as 30 or 31% of plate appearances, provided that said hitter is also able to muscle out a hefty amount of home runs over the course of a full season. This is a profound departure from earlier philosophies on hitting as it relates to the strikeout; what was seen before as a major impediment from becoming a quality major-league ballplayer is now seen as a mere nuisance, a flaw that may or may not be correctable in a hitter but can be worked around to provide production for a team.
There is still certainly a line of demarcation drawn by teams; players such as Brett Jackson of the Cubs will continue to be overlooked by their teams for as long as they post strikeout rates so high that they are impossible to work around (as exemplified by Jackson's astonishing 41% K rate during his call-up in 2012 and his career 32% K rate in AAA ball). But in the past eight to ten years, that line has thinned considerably. The question becomes whether or not this will remain acceptable practice, or whether teams and management will begin to attempt to shift the approach of high-strikeout, high-power hitters as those hitters age. The eyes of a baseball player do not get better with time, and often the strikeout rate increases correspondingly.
Our test case in 2013 is Adam Dunn. Dunn has long been the pinnacle and personification of the Three True Outcomes: in 7,317 career plate appearances, he has 2,066 strikeouts, 1,180 walks, and 412 home runs. He has never had a season in which he has struck out in fewer than 25% of his plate appearances. In his earlier years with Cincinnati, Dunn was able to reconcile his propensity for striking out with unparalleled power hitting; his ISO hovered between about .250 and about .300 from 2001 to 2010. Since then, however, Dunn has seen his power begin to evaporate right around the time he left the remains of his prime years as a hitter. Today, we have an Adam Dunn who has posted strikeout rates above 30% every season since 2010 (his K% was never above 28.6% before 2010), while his ISO has also declined significantly. As a result, in the past two years Dunn has .159 and .204, respectively, both far cries from his .240-.260 range average as a Red.
This season, the White Sox brass chose to try and modify Dunn's approach to the plate. This included him attempting to hit for contact more frequently, and showing less patience at the plate. If Dunn's results are any indication for future hitters of the Three True Outcomes mold, the decline will be inevitable, swift, and painful, with little chance of recourse. While Dunn had himself somewhat of a renaissance season in 2012 after his abhorrent 2011 season, this can be attributed to his ISO returning to a closer career baseline after it was a career-low .118 in 2011 (it was .263 in 2012). Aside from that, his approach to hitting remained static.
This year, however, we are seeing a regression to his 2011 season numbers through attempts to make more frequent contact with the ball. It has thus far resulted in a .147/.243/.358 slash line, with a wRC+ of 59, or 41% below league average. If in the next five to seven years, players with profiles similar to Dunn (namely Mark Reynolds, but also several other batters as well, such as Mark Trumbo or Chris Davis or Chris Carter) go through a natural erosion of skills and physical ability due to age, it seems quite likely that they will be dropped like rocks in water. While this has always been the case, the shelf life of a power hitter is routinely less than that of a more-rounded ballplayer, primarily because power is one of, if not the, first skills to erode as one ages. The high-strikeout, high-power hitters of today will become the forgotten names of tomorrow, and in an era of baseball where players are striking out more than ever, this could become a troubling issue. Those teams that live by the strikeout will likely meet their demise by the strikeout as well.
Lastly, the ramifications of this continued rise in strikeouts amongst hitters is large for baseball's oft-overlooked side, defense. With strikeouts on the rise and walks and home runs remaining a significant portion of the equation, there are fewer balls put into play overall. This means that defense, and in particular, the use of glove-first defenders at non-premium positions (i.e., outside of catcher, shortstop, perhaps second base) becomes a much smaller concern. Teams can now place more emphasis upon the offensive side of the game and neglect the defensive aspect at most of the positions on the field. This was exemplified by the 2012 Detroit Tigers, who went to the World Series on the backs of their hitters and ace pitcher Justin Verlander, despite a defense that included Ryan Raburn (4 errors in 62 games), Omar Infante (10 errors in 64 games), Jhonny Peralta (7 errors), Miguel Cabrera (13 errors), Prince Fielder (11 errors), and a catching tandem that provided for another 10 errors (Alex Avila and Gerald Laird), plus a utility infielder (Ramon Santiago, former starting shortstop for the 119-loss 2003 Tigers) who was responsible for 6 errors of his own. The Tigers were able to overcome poor defense partially due to the lack of balls put in play by hitters. Whether this in and of itself will become a new trend across the league remains to be seen, but it is certainly worth monitoring.