The Z Files: Okay, Now What?

Gerrit Cole is pleading with MLB to work with the players on a compromise.

Tyler Glasnow contends he hurt his elbow because he was forced to grip the ball tighter.

Garrett Richards completely eschewed his curveball in his last start.

Don Mattingly is sure the Marlins staff won't encounter any issues with the new regulation on foreign substances applied to the ball. 

Robert Arthur published a study on Baseball Prospectus suggesting whatever was being applied to the baseball may have been restricting its flight.

And we're only about 44 percent of the way through the season.

Fantasy managers are not a patient lot. We want to know what to do about all this yesterday. Waiting to see how things pan out is not an option.

Well, I have some bad news for you...

The smart approach is to avoid knee-jerk reactions to small samples. Sure, three and a half months from now we'll all be ruing moves we didn't make, but there is no basis to do anything other than keep on keeping on. Okay, maybe err on the side of caution with fringe pitching, but don't let a suspect game or two from an ace shape your judgment. 

Part of the impending dilemma is there are multiple forces meeting at the corner of Sticky Stuff Drive and Spot Check Avenue:

• Weather is warming, with an increase in offense piggybacking the rise in mercury
• We're still not completely sure how the ball is playing
• Injuries are at an all-time high and surely must be affecting play
• Minor-league numbers from the top prospects are likely inflated, rendering even higher than normal expectations upon promotion
• Most pitchers are just now eclipsing their innings totals from last season and there's no telling how this will influence stamina and effectiveness the rest of the season

Did I mention we're not even at the halfway point yet?

When conducting an experiment to test the effect of something, the proper protocol is to have that be the only variable. Unfortunately, that's impossible as each of the above cannot be held constant. Whatever does manifest in the coming weeks will be influenced by more than pitchers working without added grip. Sure, we'll all make guesses as to what level of the change is due to which variable, and manage our teams accordingly, but it's at best an educated guess.

Before broaching a couple of factors we all need to consider when digging into the numbers generated the next few weeks, I need to give a mea culpa and circle back to last week's Spin City and address a big omission.

The notion most of us will be pursuing will be to unearth pitchers with declining spin rates and assume they were gaining an advantage via a foreign substance. Of course, results are key, but where I was remiss last week was in explaining spin rate usually dovetails with velocity. In general, the higher the mph, the greater the rpm.

As such, simply focusing on spin rate may not tell the whole picture. You must also note the velocity, since a lower spin rate may be due to lesser velocity. Of course, that is an issue unto itself, but the chief takeaway is looking at rpm/mph gives a truer read on changes in spin rate.

As it happens, this segues nicely into a couple of new topics. Again, harkening back to my days donning a lab coat and safety goggles, in order to discern tangible change, it's necessary to know what to expect. The factors bulleted above cloud this, but it's still possible to help define what we're looking for with respect to just spin rate.

The first thing I wondered is whether spin rate remains consistent or if it changes as the season wears on. Looking at the league aggregate isn't perfect since the inventory of pitchers is different each month, but it's a starting point. Below is data from 2018 and 2019, focusing on the mph and rpm of four-seam fastballs (4S), curves (CV), sliders (SL) and cutters (CT). These are the four offerings where spin is most needed for effectiveness. The league averages are presented for each by month.

2019

2018

While it's possible the transient nature of each monthly player pool may skew the numbers, it appears spin rates are consistent month to month. Intuitively, one could argue for an increase or reduction. As the weather warms and the pitcher finds his groove, his spin increases. Alternatively, it could lessen as innings pile up. At least according to the above, neither is the prevailing occurrence. Maybe they're both happening to different pitchers and balancing out. Maybe as innings accumulate for some, the newly promoted arms keep the level consistent. Or maybe spin just doesn't change from month to month. Hold that thought; we'll circle back in a bit.

The other general question I have is, what is a normal range of spin rates? We'll no doubt witness a change, but what is within probability and what is beyond? To help analyze this, I looked at the pitchers registering the top-five spin rates in 2019 for the four pitches listed earlier. Each made at least 30 starts. The average, high, low and standard deviation was determined for the 30-something outings.

Four-seam fastball

Curveball

Slider

Cutter

Concentrating on the numbers and not that there are some repeat names, it should take a triple-digit difference to raise a red flag. In fact, the ranges for the three breaking pitches are quite vast, which will serve to complicate analysis.

That said, I have a confession. I really don't know how to apply the data. How many games at a lower level are needed to trip the alarm? Should we be looking for differences on the order of one or multiple standard deviations? The good news is the industry is replete with many people better versed in this style of analysis, so I'll be keeping an eye out for the answers. Still, it's nice to have a foundation when learning how to apply the data.

OK, let's check out the monthly spin rates of those listed above to determine whether individual pitchers incur spin rate differences over the course of the season.

Four-seam fastball

RPM

MPH

RPM/MPH

I'll be honest, I expected a drop in both velocity and spin rate over the course of the season. What is it they say about assume? There certainly doesn't appear to be a significant four-season spin rate change attributable to anything other than variance.

Curveball

RPM

MPH

RPM/MPH

Slider

RPM

MPH

RPM/MPH

Cutter

RPM

MPH

RPM/MPH

There are some eyebrow-raising observations here, but in general it appears unless something fishy was done, velocity and spin rate remain consistent over the entire season.

The main oddity involves Gray's and Buehler's curve and slider numbers showing an increase later in the season, but that's a story for another day.

Summary

It appears a drop in spin rate can be ascribed to no longer using one's sticky substance of choice. 

However, it's currently unclear (at least to me) the extent of decline needed to be considered significant, as breaking pitches exhibit ranges of several hundred revolutions over the course of the season.