Will the single-game pitcher strikeout record ever be broken?

The answer to this question is (probably) yes.

As you can see in the graph above, the rate at which starting pitchers have recorded strikeouts has been increasing steadily since the early 2000s. In the year 2000, the league average strikeout rate for starters was 15.8%. In 2019, it was 22.3%, an increase of over 40 percent.

………

Four pitchers have recorded 20 strikeouts in a single-game of nine innings or fewer (on September 12th of 1962, Tom Cheney struck out 21 hitters, the catch being that he did so in 16 innings).

• Max Scherzer (5/11/2016 vs DET)
• Randy Johnson (5/8/2001 vs CIN)
• Kerry Wood (5/6/1998 vs HOU)
• Roger Clemens (9/18/1996 vs DET and 4/29/1986 vs SEA)

Given that the league average strikeout rate will likely continue to climb, one has reason to believe that a pitcher will eventually strike out more than 20 batters in a game.

Here are the qualified pitchers with the highest K/9 since 2018…

1. Gerrit Cole (13.13)
2. Max Scherzer (12.44)
3. Justin Verlander (12.15)
4. Jacob deGrom (11.20)
5. Trevor Bauer (10.99)

While one may feel optimistic that the record will be broken someday, it is important to consider that starters are not going as deep into games nowadays, as depicted below.

Gerrit Cole presently represents the best chance of the record being broken. To determine the feasibility of Cole striking out at least 21 batters in a start, I first calculated the mean and standard deviation of Cole’s strikeouts since 2018.

Mean: 9.26 strikeouts

Standard deviation: 2.88 strikeouts

Then, I ran 10,000 simulations of his starts using a normal model.

Here were Cole’s highest single-game strikeout totals…

1. 21.8
2. 20.3
3. 19.4
4. 18.6
5. 18.5
6. 18.5
7. 18.4
8. 18.2
9. 18.2
10. 18.1

Of the 10,000 simulations/starts, Cole struck out 21 batters or more only once.

At his current talent level, you’d expect Cole to strikeout 20 batters or more in approximately in 0.02% of his starts (1 in 5,000).

In other words, the chance of Cole breaking the nine-inning (or less) strikeout rate is improbable to the say least.

Here is a histogram of the 10,000 simulations…

The most common strikeout total for Cole was nine, which is to be expected considering his mean strikeouts over the course of the last seasons was 9.26.

Gerrit Cole isn’t going to remain a strikeout machine forever, and he definitely isn’t going to make 5,000-10,000 more starts in his career.

The strikeout record may never be broken. It presumably won’t be broken anytime soon.