The True Value of Strike One (F-Strk%)

It’s been said – many times and many ways – that strike one is the most important pitch in a hurler’s arsenal.  And I’m certainly not the first writer to explore that notion.  But as I undertook my annual winter task of studying my spreadsheets of pitching statistics – or more than 15,000 data points on over 10 pages – I wondered how much significance that first-strike percentage has on other stats we care about in fantasy baseball.

So I broke it down. My intent was to study its effect on ERA.  ERA as we know is fickle; it’s subject to BABIP, defensive prowess behind the pitcher, shifts, exit velocity, etc… But I started my study convinced that ERA would be affected by a good F-Strk% and hurt by a poor performance. I looked at pitchers who logged at least 120 IP in 2019, a group that gave me 93 pitchers.  (Let that be our first lesson, that each major league team averaged only 3 pitchers who threw even just 120 innings.)

It also made sense to look at K/9 and BB/9 – If you’re ahead of hitters, it figures that you’d strikeout more and walk fewer.  Let’s look at the numbers from last season:

2019 120+ IP F-Strk % ERA xFIP K/9 BB/9
Overall (93) 62.24% 4.05 4.29 8.78 2.77
Top 20% F-Strk (19) 67.22% 3.90 3.99 9.18 2.13
Middle 60% (54) 62.49% 4.03 4.27 8.94 2.79
Bottom 20% (20) 57.47% 4.25 4.58 7.96 3.33

Okay – so our top 20 percent F-Strk% pitchers did better in ERA, though not quite to the degree I expected, and the strikeout and walk numbers make a lot of sense. And a spread of 0.35 in ERA – from top 20 percent to bottom 20 percent does make a big difference on your fantasy team.

My list did reveal that seven pitchers in this group of 19 in the top 20 percent had ERAs over 4.00 and Rick Porcello’s 5.52 didn’t help.  I noted that Tyler Mahle’s 5.14 ERA came with a 3.99 xFIP, so I made a mental note to study his statistics more deeply later. He owned the fifth-highest F-Strk% (68.5).

Because my spreadsheets contain 3-year data for hurlers at or over 120 IP, I run the numbers on the 2018 arms who tallied that workload. Here’s the summary:

2018 120+IP F-Strk % ERA xFIP K/9 BB/9
Overall (105) 61.92% 3.90 4.01 8.58 2.89
Top 20% F-Strk (22) 67.06% 3.33 3.51 9.24 2.15
Middle 60% (62) 61.94% 4.00 4.02 8.59 2.90
Bottom 20% (21) 56.46 4.23 4.50 7.83 3.61

Overall, K/9 and BB/9 were a touch worse (for the pitchers) yet the average ERA was much better. (Well, that’s baseball Suzyn). But, wow! The ERA of the top 20 percent was much lower, by more than a half-run, than in 2019.

The top 20 percent group included just four arms who surrendered ERAs of 4.00+ and I reminded myself we’re dealing with small groups and data sets. But the ERA drop from 2019 (or more accurately the raised ERA of 2019 over these levels) was notable and I was curious about the 2017 data.  So far the first-strike ability of pitchers was consistent in determining K and BB totals, at least among the separate groups.

So to 2017 I went:

2017 120+IP F-Strk % ERA xFIP K/9 BB/9
Overall (103) 61.97% 4.15 4.23 8.22 2.98
Top 20% F-Strk (20) 66.02% 4.10 4.02 8.59 2.32
Middle 60% (62) 61.21% 4.14 4.20 8.31 2.97
Bottom 20% (21) 56.32% 4.25 4.54 7.60 3.62

Another wow. The top 20 percent group was merely slightly below average and above a 4.00 ERA. My sense is that BB/9 is the most predictable stat from F-Strk % with K/9 slightly behind.  But ERA is a toss of the dice at this point.

Overall ERAs for the 120+ IP group went from 4.15 in 2017 to 3.90 in 2018 and up to 4.05 in 2019. And the 3-year “trends” for the top 20 percent group (4.10/3.33/3.90) leaves me with no answers ultimately about throwing strike one and a pitcher’s ERA. 

I did notice that pitchers improved K and BB totals each year which *should* assist the ERA question overall but not directly or significantly.

Next, I wondered if pitchers who most often threw first-pitch strikes were also among the top players in Zone%, or the percentage of pitches thrown within the strike zone.   Here’s the year-by-year tally of arms who were in the top 20 percent of F-Strk% and Zone%:

Year In Top 20% Of F-Strk% and Zone%
2019 7 (of 19)
2018 11 (of 22)
2017 9 (of 20)

Okay, 44 percent of the pitchers made both lists over the 3-year period. Not a shock there. After all there are fewer than 4 pitches per at-bat on average, so getting strike 1 is a pretty good indicator you’ll be in the zone more often than not.

But, the more interesting search was for the pitchers in the top 20 percent in F-Strk% and the bottom 20 percent of Zone %.  I wasn’t sure I’d find any names, but sure enough there were a small handful:

2019 (1 pitcher) F-Strk% Zone%
Zack Greinke 67.3% 39.1%
2018 (3)    
Alex Wood 69.1% 39.5%
Mashahiro Tanaka 68.2% 39.8%
Zack Greinke 67.0% 38.5%
2017 (1)    
Johnny Cueto 64.5% 40.3%

Note: In 2017, Greinke was in the bottom 20 percent of Zone% again, but only 62% F-Strk%.

So for Greinke, it’s a skill: Get ahead of the batter and then be coy and around the plate but not often in the zone. Tanaka’s approach is similar.  Johnny Cueto just doesn’t know where the hell the ball is going.

Naturally the next question should be: If Greike is so often among the bests in F-Strk%, it must be a repeatable skill, not just a random stat. So I tabulated how many pitchers also repeated in the top 20 percent in the category.  Remember, these are pitchers with at least 120 IP, not all pitchers.

The players who made the list each of the 3 seasons:

Chris Sale
Clayton Kershaw
James Paxton
Mashahiro Tanaka
Max Scherzer
Rick Porcello

Players who made the list in two seasons:

Alex Wood
Jose Quintana
Kyle Hendricks
Luis Severino
Marco Gonzales
Miles Mikolas
Zack Greinke

And those who made the list last year, in order of F-Strk%:

Player F-Strk%
Chris Paddack 71.3%
Max Scherzer 70.3%
Madison Bumgarner 69.6%
Mashahiro Tanaka 68.8%
Tyler Mahle 68.5%
Zach Efflin 68.1%
Rick Porcello 67.6%
Clayton Kershaw 67.4%
Zack Greinke 67.3%
Kyle Hendricks 66.4%
Chris Sale 66.0%
Mike Clevinger 65.9%
Noah Syndergaard 65.8%
Zack Wheeler 65.8%
Marco Gonzales 65.7%
Miles Mikolas 65.7%
Walker Buehler 65.7%
James Paxton 65.6%
Joe Musgrove 65.6%

Aside from the usual suspects, we see Syndergaard join the list and Paddack topping the list in his rookie year. Remember he was shut down early to protect his arm. Buehler is already on the shortlist of superstars whether you realize it or not and Mahle, Efflin and Musgrove are interesting names worth further study.