Pitcher Velocity and the Aging Process

Sometimes just investigating things a bit can lead you to interesting conclusions. You get to read the result of my investigation that occurred over the last week, but the truth is that it started with a very different thesis than it ended up with. It all began when I compiled a list of what I thought might be viable trade targets in one of my roto leagues. I have one of those teams perfectly unbalanced. In this case it’s all hit and no pitch. So I pulled a list together with the starting pitchers from teams with the exact opposite problem. You can make trades that win for both teams if you’re realistic. You just need to put a little work into it.

Once the list was completed, I needed to figure out who I could target that I thought a manager would be willing to trade to me for what I was willing to give. I’m not getting Clayton Kershaw for Denard Span, so what are the viable trade packages? However, I still want to see if I can get more than my Span dollar is worth, so I needed to dig into the data and see if there was someone underperforming who could turn their performance around.

One lesson to remember when playing the trade for regression game in fantasy baseball, is that in a given season hitters are much more likely to regress positively to expectations than pitchers do. Some of that is due to the number of events, or at-bats versus innings pitched, and some of that is just due to pitchers being inherently more volatile relative to our forecasts. So when I look at pitchers who have been underperforming, I tend to be much more critical and look for underlying problems that might portend a trend change versus random events. One of those tools is a change in pitcher’s velocity.

The old school thought likes to play this down a lot. You’ve probably heard the chorus on broadcasts saying that CC Sabathia and the decline in his velocity is nothing to worry about. Now he just needs to learn how to become more of a pitcher to stay effective etc… It certainly is true that there are pitchers with less velocity that can be very effective. However, there does seem to be a tipping point at around 90 MPH. Fewer pitchers with fastball velocity below 90 are able to stay effective. If you want a reason to worry, then go look at Roy Halladay’s two-seam fastball velocity and xFIP trends the last three years. Steamer Projections have significantly improved forecasts for pitchers, and the primary reason why is that they incorporated pitcher’s velocity into the formula. It doesn’t mean a pitcher can’t be effective at lower velocities, but it does mean the threshold between success and failure is a lot thinner. The result is that you see fewer pitchers stay successful below 90 than above it.

That was the story to how this all began. The result is that I looked at my list of 25 starting pitchers, and only 4 of them didn’t have their average fastball velocity decline this year versus last year. That’s an 84% rate of starting pitchers seeing velocity declines. So what was going on here? Did I just have a random sample? A figure of 25 didn’t seem that small considering there are approximately 85 in the total league. Not to mention that these were the teams that had good pitching stats!

The first thing I wanted to see is if this was a characteristic across all of baseball this year. I decided to use all starting pitchers that qualify for leader-board stats. This way I have a pool that throws a lot of pitches and tends to be more consistent year to year in composition than their relief corps mates. I then calculated the mean average and the median average for the entire pool. Here are the figures and their rate of change year over year:

At this point I’m starting to wonder what’s going on. Has something changed with the pitchFX readings that we don’t know about? How sweet would it be if I discovered a conspiracy! (Diabolical voice)

I started to look into the pool of players and see if there had been a style change creeping into the ranks of league pitchers. So I made a list that comprised only the starting pitchers who qualified for each of the last three seasons. This way I thought I could eliminate any new pitchers that were skewing the overall figures. The first thing I found was that the rate of change was essentially the same with a bit more volatility due to the smaller sample. The second thing I found was that Sabathia had the largest decline of any pitcher on the list. Here are the top 10 starting pitchers in terms of vFA declines from last year:

It was at this point that dawn broke over the marble slab, and the obvious answer hit me in the face. I realized that my smaller sample comprised only of starters that qualified for the last three years in a row had a built in bias. All of those pitchers would obviously be a year older each year. So in order to see if their declines in velocity were significant, I needed to figure out if they were greater than what we should expect from an average pitcher as he ages. This is the answer, and it led me to check the entire pool of qualifying starting pitchers.

Sure enough the average age of the pool has ticked up this year. Now we can check to see if the degree of decline in velocity is in line with what we should expect. I pooled all three years of data together and sorted them out by age. What you’ll see is that there are two periods in particular where a starting pitcher’s velocity usually declines: age 29, and 32-33.

As you can see on the bottom part of the chart, the rate of decline we should expect for the average of all three years is about (1.8%). With the average age increase by .3% this year to almost 29, we should expect about a (.54%) decline in fastball velocity. That figure pretty closely matches the actual decline of (.44%) that we’ve seen. So all is explained, and everything in the world of pitchFX is functioning correctly, (drat). What does this all mean for Sabathia looking forward?

Sabathia has hit the tender age of 32 this year, and as you can see on that chart above, it means he’s hitting the second major zone of velocity decline for starting pitchers. His (2.3%) decline is materially greater than the average, but this data is limited. Note that the figure in 2012 for 32 years old went up which skews the average. We also know that Sabathia has had more use in terms of innings pitched than your average starter to this point. The good news is that he’s still a tick above the average fastball for his age. The bad news is that the decline might not be over. He may lose more velocity next year that would take him below that 90 threshold.

Velocity is important, and it’s one of the reasons why the list of qualifying starting pitchers gets so small in the 33 and above camp. Here is this year’s list of those pitchers:

I’m guessing no one out there had Jeremy Guthrie as the fastball velocity leader out of this group. There are only 16 names on this list, and only 5 of them can break 90 still. It becomes apparent how limited this investigation is, when considering the likelihood of Sabathia remaining effective as he hits this key stage of his ageing process. There are a lot more questions regarding how a pitcher’s arm ages in terms of stress and strength, as opposed to just using age as a proxy. Having said that, age has been a very good all be it simplistic way of answering those questions.

I don’t think anyone can answer with any great certainty whether or not Sabathia will be effective in post 32 years. When I look at that list above I see some diversity, but the majority are pretty much finesse control guys at this stage of their careers. In fact, I think you could argue that most of these guys that are continuing to have success at their advanced age, have always been mostly finesse control style pitchers. Bartolo Colon, and perhaps A.J. Burnett, might be the exception to that statement, but clearly Sabathia is likely going to have to continue to change his style of pitching if he’s going to remain effective into these advanced years.