It used to be that striking out a batter an inning (or 9 K/9, as we used to abbreviate it in the days prior to the Internet...) was a Big Deal. Not so much anymore.
While it's not quite gotten to that for the next step up that ladder (10 K/9), it's definitely moving in that direction.
There are now nearly eighty instances of a starting pitcher exceeding 10K/9 for at least 60 IP in a season (we'll explain that limit in a minute), with nearly three-fourths of them occurring since 1990.
Our handy "year chart" shows the distribution over the years since 1959, when Sandy Koufax was the first pitcher to crack the 10K/9 barrier.
As you can see, the number of instances has increased sharply in the past two decades. It appeared to be leveling off a bit thus far in the 2010's, projecting to around 25 for the decade, until the current glut of starters (nine in all) who are currently on pace for a 10K/9 season.
Those nine pitchers are (in descending order of K/9): Clayton Kershaw, Yu Darvish*, Stephen Strasburg*, Jake Odorizzi, Chris Sale, Masahiro Tanaka, Max Scherzer, David Price, Corey Kluber.
(The guys with * are the ones who already have at least one 10K/9 season under their belts.)
We picked 60 IP to get all of the starting pitchers in 2014 who are looking to be on track to qualify for the ERA title, and by doing so we did pick up some short seasons from the past: two from Sid Fernandez (1995, 1996: both under 100 IP) and Tony Cingrani from last year (104 IP).
Which pitchers are on this list the most? You may not be surprised to discover that the king of this stat is The Big Unit (aka Randy Johnson). He pulled off this feat twelve times: first time in 1991, last time in 2004.
Nolan Ryan is next with eight. Then it's Curt Schilling and Pedro Martinez (five); Mark Prior and Koufax (four); Yu Darvish, Hideo Nomo, Kerry Wood, and (if he keeps it up this year) Max Scherzer (three).
Overall record of the pitchers on this list (including the nine guys from 2014): 1175-663 (.639 WPCT), 3.04 ERA.