THE BOOK--Playing The Percentages In Baseball

I think it’s been shown that velocity from pitchers has improved considerably.  I think it’s up to nearly 92 MPH for the average pitcher.

Regardless of the reasons behind a change in run scoring, how should such changes be incorporated into run expectancy calculations? Or, perhaps more precisely, how much data to provide a basis for making an adjustment?

Nick/1, I found this from 2002-2009 BIS data:

That includes cut fastballs, which drops the average fastball speed by a few tenths of a mph.

I haven’t run any similar data for 2010.  Have you, or have you seen that anyone else has?

I have some league-wide PITCHf/x data from April 2010 that suggests that the league-average fastball speed was about a quarter mph lower than the average for the full season in 2008-2009, after applying a temperature adjustment.

I don’t know whether it’s normal for the lg-avg fastball speed to be lower in April or not, after adjusting for the cooler temperatures.  In 2008 it was almost a half mph lower in April, but in 2009 there was no difference between April and the rest of the year.

As I look at this data, I also notice that I’m not seeing the big (0.5 mph) difference between 2008 and 2009 in the PITCHf/x data that I (and others) have observed in the BIS data.  It’s more like 0.1 mph.  Hmm.  MGL had suggested looking at this after I published my article on fastball speed effects, but I didn’t realize I already had that data lying around.

Oh, but that data is temperature-adjusted, and I suppose I should not assume that the average temp was the same in 2008 and 2009.  Okay, it turns out it was a little warmer in 2008, by about one degree Fahrenheit.  That doesn’t make much difference when I back out the adjustment for that.

Apologies and just in case there is any uncertainty: That last sentence should read, “… how much data are needed to provide a basis for making an adjustment?”

Mike: no way would I look at those numbers without first verifying the data quality. 

Look at the year-to-year numbers of pitchers at age 21-29 (maybe 23-32?) who pitched in back-to-back years .  Report those numbers.  This is the control group, and it should be flat.  If we see a spike in 2009, then I question that the speeds are measured from the same basepoint each year.

Tango/5, I covered this much more fully in that old article:
http://www.hardballtimes.com/main/article/lose-a-tick-gain-a-tick/

There is a section where go into great depth abou that topic.

The same group of pitchers in back-to-back years was very close to flat (within +/-0.1 mph, I don’t remember exactly).  It was the pitchers entering and leaving the sample that were changing the average.  The 2008-2009 time period saw a lot of slow fastball pitchers retiring (Glavine, Maddux, David Wells, etc.) and a lot of young flamethrowers entering the league. 

So the BIS data seemed to be consistent when I examined them.

However, I was just reflecting on that now that I was taking a look at league-wide PITCHf/x fastball speed data in light of this thread.  The PITCHf/x results do not seem consistent with the BIS results.  I have not done any further investigation as to pitcher samples in the PITCHf/x data.  That is something I may do, but probably not in the immediate future.

Here is the relevant section of the article:

I looked at the change in fastball speed for starting pitchers from 2007 to 2008 and from 2008 to 2009, grouped by team. The deviations by team largely fell within +/- 0.5 mph. If there was a reporting bias due to PITCHf/x, one would think that the increase for the teams displaying PITCHf/x would be higher than the league increase of one mph. In fact, those teams known by me to be displaying PITCHf/x speeds did not show any tendency to be at the higher end of this distribution. Moreover, the average increase in fastball speed for the whole group was slightly below zero!

Wait, didn’t I just say that the average fastball speed for the league had risen by about 1 mph between 2007-2009? Yes, I did. But as Dan noted in his article, “The identities of the pitchers in the sample change from year to year.” That turns out to make a great deal of difference. When you hold the identities of the pitchers constant, average fastball velocity stays pretty close to flat from year to year. This is true for both starters and relievers.

Why, then, did the league’s average fastball speed jump so much in the last couple years? The answer turns out to be in the pitchers entering and leaving our sample each year. Starting pitchers dropping out of our sample averaged 87.8 mph, while starting pitchers entering our sample averaged 89.7 mph, until 2009 when the starting pitchers entering the sample averaged 90.4 mph.

The 2009 season saw a bevy of new hard-throwing starters: Felipe Paulino (95 mph), Jordan Zimmerman (93), Vince Mazzaro (93), David Hernandez (93), Brett Anderson (93), Derek Holland (93), Tommy Hanson (92), Jason Berken (92), and Ricky Romero (92). On the other side of the ledger, a number of softer-tossing starters left the league after 2007 or 2008: Tom Glavine (82 mph), Greg Maddux (84), Mark Redman (84), David Wells (85), Kenny Rogers (85), Steve Trachsel (85), Mike Mussina (86), and Matt Morris (86).

And MGL’s comment:

This is all based on the BIS data?  When you were wondering if BIS might be biased from year to year, why didn’t you use pitch f/x to see if that was true?  After all, you are also the pitch f/x man!

And my response to him:

MGL, yes this is all based on BIS data.  I had done a similar investigation a year or so ago based on PITCHf/x data that came to similar but much more limited conclusions, but I didn’t include any of that in this study.  The BIS data covers many more years at this point than does PITCHf/x.

The simple answer to your question is that I simply didn’t think about looking at PITCHf/x to double check the 2007-2009 velocity increase.

It seems obvious now that you say it.  I suppose the reason I didn’t has something to do with the fact that I didn’t come to the conclusion about velocity increase from 2007-2009 exactly the way the logic is presented in the article.

I came across the Dan’s article and the cutter explanation after I had already done a fair amount of investigation into the matter.  Adding in the cutter correction made it obvious that the increase had happened mostly in 2007-2009; that was not so obvious to me before that.

You make some interesting comments at the Book blog, particularly about an increase in overall MLB fastball velocity implying an overall increase in pitcher effectiveness, which might be responsible for depressing run scoring.  I had viewed the question of average MLB velocity as an aside to my research and a sanity check, but that puts it into the realm of something that merits further research in its own right.

A couple of weeks ago, I did aging curves on fastball velocity from the FG BIS data.  For starters, it was almost perfectly linear downward from age 21 or so, to the tune of losing about .2 mpg per year.  Not quite linear, as I said.  From 21 to 31, they lost around .12 per year and then like .34 per year after that.  The regression formula was y = -0.0015x3 + 0.0408x2 - 0.4657x + 0.6277 with R² = 0.9776.

For relievers, the curve was completely different.  It was flat from age 21 to around age 29 and then straight down from there to the tune of around .25 to .3 runs per year.  The regression formula is: y = 0.0003x4 - 0.0155x3 + 0.243x2 - 1.4945x + 0.5983 with R² = 0.9043.

I am guessing that starters lose velocity at such an early age and relievers don’t because they pitch so many more IP per year and perhaps get injured more, but there could be other explanations, including the usual selective sampling issues we have when it comes to aging curves.

All pitchers combined show an almost linear curve downward to the tune of around .14 mph per year.

Could it also be that starters learn to manage their endurance better as they age, and don’t throw fastballs as hard as they can? Relievers probably continue to throw as hard as they can in all situations.

One way to look at this would be to focus on fastball speeds in high leverage situations - when starters and relievers are presumably following similar strategies.

Ken, sure, could be…