On Wednesday night, Red Sox ace Chris Sale made a bit of history, becoming the first American League pitcher to tally 300 strikeouts since the turn of the millennium, and just the fourth since the adoption of the designated hitter in 1973. While the 28-year-old southpaw's case for the AL Cy Young isn't as strong as it was a couple months ago, he's joined some elite company.
At Camden Yards, Sale spun eight shutout innings against the Orioles, allowing just four hits without a walk and matching his season high of 13 strikeouts. The last of those came on his 111th and final pitch of the night, a slider that caught Ryan Flaherty looking. The whiff was his 300 for the season, making him the first AL pitcher to reach the mark since the Red Sox's Pedro Martinez in 1999. Since then, the only pitchers to strike out 300 have hailed from the NL, where pitchers bat: the Diamondbacks' Randy Johnson (four times, annually from 1999–2002) and Curt Schlling (2002) and the Dodgers' Clayton Kershaw (2015).
As with other single-season milestones such as 20 wins and 250 innings, the disappearance of the 300-strikeout season owes plenty to the reduced workloads of starters via the industry-wide adoption of five-man rotations, increased reliance upon bullpens at the expense of complete games, and the use of pitch counts and (for younger pitchers) innings caps as a crude attempt to prevent injuries. In the 18 seasons since Martinez struck out 313 hitters (in just 213 1/3 innings), only nine times has a pitcher thrown at least 250 innings, and only three times has one made more than 35 starts.
While pitcher workloads have decreased during this millennium, strikeouts have been on the rise continuously since 2006, as I pointed out in connection with this year's record number of home runs. This will be the 12th consecutive season that MLB sets a new record for total strikeouts, with the figure topping 40,000 for the first time. The analytic revolution has reduced the stigma against the K, finding that in most cases, for hitters the strikeout is just another out. It’s preferable to grounding into a double play, and generally correlated with greater power at the plate. For pitchers, K’s have far more value, and with the reduction of the starters' workloads has come a parade of relievers pitching with maximum effort for one inning at high velocity, further boosting strikeout rates.
Thus, it's worth putting Sale's accomplishment into context, at least among the other 300-strikeout seasons. A total of 16 pitchers have reached the plateau 35 times since 1901, just five of which came prior to the majors' first-wave of expansion in 1961-62. As with ERA+ and OPS+, we can index a pitcher's strikeout rate to the league rate (both expressed in terms of strikeouts per plate appearance), with 100 being league average, and every increment in each direction representing a one percent difference. That means 120 and 80 would respectively indicate pitchers striking out hitters 20% more or less frequently than the league average. Unlike ERA and OPS, I'm foregoing park effects for the sake of simplicity here, but this at least puts the leagues on the same footing, whether or not they have the DH. Call the stat K+, one I've begged the folks at Baseball-Reference for, again and again.
Sale has whiffed 36.3% of all batters faced in a league where 21.3% is average, for a 171 K+. Of the 35 300-K seasons, that's actually at the lower end, but the company is still quite impressive:
2017 Red Sox
Here's what the top 10 looks like:
1999 Red Sox
In 1999, Martinez struck out hitters at more than twice the league rate, whereas Sale is not quite to doubling it. Still, the latter’s season outranks three of those by Hall of Famers, namely Koufax and Carlton; someday, both Kershaw and Schilling will be enshrined as well. All of the top 10 seasons were produced by Hall of Famers, as were the majority of the 15 that land in the middle of those two tables: five more by Randy Johnson, two by Walter Johnson, and one apiece by Koufax, Martinez and Ryan.
So Sale's season isn't as impressive as Martinez's by this measure, but then the latter's season is one of the greatest in any context; his 243 ERA+ that year ranks eighth since 1901. In 2000, when Martinez set a record via a 291 ERA+ (1.74 in a league where 4.91 was average), he also produced a 221 K+ (284 strikeouts, a 34.8% rate in a league where 15.7% was average). As that season illustrates, it's possible to have an impressively high K+ without reaching 300 strikeouts. Indeed, the top two pitchers of all time in terms of strikeout rate (K/PA) dominate the top 10 for the wild card era (1995 onward) among ERA qualifiers (one inning pitched per team game scheduled):
1999 Red Sox
2000 Red Sox
Johnson's 1998 season is weighted by the number of batters faced in both leagues (he was traded from the Mariners to the Astros at the deadline). That season bumps Martinez's 186 K+ from 2002 out of the top 10. Sale's 171 ranks 23rd during the wild card era, but it's second since 2006, the beginning of the period during which K rates have continuously risen. He’s not the only representative from this season:
2017 Red Sox
2015 White Sox
2007 Devil Rays
2014 White Sox
2009 Red Sox
2007 Blue Jays
Sale's top rival for AL Cy Young honors, Corey Kluber, cracks the top five; the Klubot has racked up 252 K's this year in 191 2/3 innings, and might have reached 300 if not for a four-week absence in May due to a lower back strain.
Of course, there's more to winning a Cy Young award than just strikeout rate, and via a mini-slump—a 3.69 ERA and 2.94 FIP since August 1, compared to 2.37 and 1.92 prior—Sale now trails Kluber in ERA (2.35 to 2.75) and ERA+ (195 to 164), though he leads in FIP (2.22 to 2.49). The two pitchers are tied for the league lead with 17 wins. Via Baseball-Reference's version of WAR, which is driven by runs allowed, Kluber leads Sale, 7.6 to 6.2, but via FanGraphs' version, which is driven by FIP (an ERA estimator based solely on strikeout, walk, hit-by-pitch and home run rates, all of which are defense-independent), Sale leads 8.2 to 6.9. I tend to strongly favor bWAR for pitchers because the past decade and a half. Since Voros McCracken's Defense Independent Pitching Stats theory was introduced, that metric has taught us plenty about the value of sequencing and pitchers' differing ability in producing weak contact, but from here, either pitcher appears to be a reasonable Cy Young choice.
With both Sale and Kluber looking to the postseason now that their teams have clinched playoff berths, we may not get much in the way of further separation, so the voting could be a tossup. But whether or not he brings home the hardware, Sale has had a season for the ages.