Lookout Landing

Not sure I understand this.

I understand that you could have a K/9 of 9 by striking out one batter per inning but have varying strikeout percentages because the batters faced would be different. Say in a 9 inning game, seeing only 27 base runners would be a 33% strikeout rate whereas facing 40 batters in the same 9 inning game would only be a 23% strikeout rate.

What I am trying to figure out is how defense effects K/9.

If a pitcher's defense makes more outs on balls in play, the pitcher has less opportunity to strike batters out

Let’s say we’re playing the Twins and Felix is pitching with two outs. Joe Mauer hits a line bullet to center field.

In Scenario A, Franklin Gutierrez makes a great diving catch, robbing Mauer and ending the inning
In Scenario B, the ball falls in front of Jeremy Reed, and Felix strikes out Jason Kubel to end the inning.

If we assume that all other outcomes are equal besides these two, Felix will always have a higher K/9 in Scenario B since K/9 is based on innings pitched, and we know that innings pitched is partially a function of defense.

A shitty defense allows the pitcher to face more batters per inning, meaning you could have a higher K/9

even though your K% would be the same or lower.

marc w - September 30, 2009 reply

Speculation

More outs resulting in non strikeouts lowers the chance of any of the 3 outs in an inning (or 27 outs in a game) from being strikeouts?

Wouldn’t that also effect strikeout % tho? Since, theoretically, a stronger defense would turn more balls in play into outs, wouldn’t that be fewer batters faced overall and / or fewer batters faced that result in strikeouts? Or is the percentage not effected as strongly as it is for inning based rates?

This is true as well, but adding to the numerator will always make a bigger difference than adding to the denominator

essentially, adding that extra strikeout in the numerator of K/9 will make a much larger difference than the reduced at-bats for the K% calculation.

Ah, I see what you mean.

Teej - September 30, 2009 reply

K% is not affected by defence

How is that?

Speculation 2:

Pitcher A faces 30 batters in a 9 inning game and strikes out 4.
Pitcher B faces 30 batters in a 9 inning game and strikes out 6.

The difference was two exact same foul ball plays that pitcher A’s team got but pitcher B’s team dropped, forcing pitcher B to record two more strike outs. Pitcher A records a 20% strikeout rate while Pitcher B has a 13%.

This isn’t theoretically possible?

Small sample size

you assume over the course of a season that even if the defense is excellent or shitty, the pitcher has ~the same chance to strike out any given batter.

Well of course. I'm merely speaking hypothetically.

It didn't 'force' pitcher B to do anything

Okay.. different term...

Allowing Pitcher B another chance to strike those batters out. Whereas Pitcher A had plays made for them on balls in foul territory.

The extra strikeouts don't come from the defence dropping the ball, they come from the pitcher striking the batter out

Foul balls are a weird non-PA ending defensive chance that I hadn’t really thought about, but the point holds. K% is the measure of skill, K/9 is not

And if pitcher A and B were equally skilled in getting strikeouts, one would expect an extra quarter of a strikeout for B

I agree with the conclusion.

I realized that the only situation I could come up with wherein the defense could be a factor was on foul balls in play. Then i started wondering about whether stadiums with larger foul areas would make that situation more likely, since there’s more ground to cover and a greater chance at making plays on foul balls.

Perhaps I’m just thinking about it too much.

Jeff Sullivan - September 30, 2009 reply

K% is a probability, K/9 is not

Good defense lowers your K/9 because you face fewer batters, since your fielders are making outs.

Put it this way: If you get a ground ball that your shortstop makes the play on, you only have two more possible outs this inning to get a strikeout. If the shortstop muffs the ball, you have three more opportunities.

Teej - September 30, 2009 reply

Expand K/9

The denominator is 27*Outs, or 27*PA*[1-(K%+BIP*DER)]

Manzanillos Cup - September 30, 2009 reply

David gets asked this a lot

And his answer, for better or worse, is that it doesn’t really matter, so he has no incentive to change it. There’s no difference in projecting future strikeout performance whether you use K/9 or K%, which is what 99% of all applications of the statistic are for.

davidcameron - September 30, 2009 reply

People hate change

Matthew - September 30, 2009 reply

That is one way in which the Hardball Times' K/G is kind of nice

It’s essentially K%, but normalized to a scale similar to K/9. If you started using K/G, most people probably wouldn’t even notice until they saw some discrepancy between K/9 and K/G, at which point it becomes necessary to explain why weighting things per batter makes more sense than weighting things per inning.

ubelmann - September 30, 2009 reply

Why do people like nine innings as the denominator for individual pitcher stats so much?

This has always bugged me about RA and ERA. Nine innings is kind of a convenient arbitrary standard, because nine innings per game and all (which makes sense when you’re measuring team stats), but starting pitchers throw complete games about 3% of time these days. RA is not a good estimation of the number of runs a SP would give up if he had to throw 9 innings per game.

I think it would be cool if a starting pitcher triple slash line caught on – (IP/GS) / (R/GS) / (K/GS). Context is easy for a casual fan to grasp, and gives you a good idea of what you’re likely to see in the box score after the start. It’s not K%/BB%/GB%, but I could go for it as a “mainstream” stat.

It isn't a big deal in most cases and it's more inuitive

vivaelpujols - September 30, 2009 reply

It's only more intuitive because people are indoctrinated into it