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Note: About 95% of this article was finished before the news that MLB is going forward with a 60 game season.  I finished it knowing that more imporant work needs to be done. This series now comes to an abrupt end and I will return to the series once the season is over one way or the other.

I’m continuing my quest to predict pitcher injuries and their effects as best as possible. I started grinding through the process last week and found through some additional work that injuries from just the past two seasons drag down production. Today, I’m going to go over some other possible other injury causes and provide updated injury ranks.

While I’ve done quite a bit of my own work on pitcher injuries, I decided to scour the web come up with some new ideas. Here are some possible ideas ranked by how I’d like to investigate them.
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With so much sabermetric work already completed, I’m creating a ton of work for myself to see if a hitter’s athleticism influences how they age? Additionally, do these “athletes” age better? I tried to jump the gun a few nights ago with an ill-fated Twitter thread where I thought about reverse-engineering the stats. Instead, I’m going to put a value on a hitter’s athleticism using some readily available metrics.

I began my search by using some advice from Bill James who commented on my Tweet.

Let's assert as Point A that "athleticism" consists of four things: Speed, strength, agility and quickness. "Strength" is the most troublesome, because you can have strength in many different body parts, and people who are strong in one area may be relatively weak in others.

— Bill James Online (@billjamesonline) June 7, 2020

He just rattled the traits off and since he’s likely forgotten more about baseball than I’ve ever learned, I’ll just focus on them. I’m guessing he’s already investigated the subject.
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Projecting pitcher injuries and their effect seems like the Holy Grail for fantasy analysis. From years of research on the subject, I find it’s just a frustration filled enterprise with no firm resolution. Until a start to the 2020 season has been agreed upon (or I eventually find an acceptable answer), I plan to continuously grind for a workable understanding of pitcher injuries.

First, this article will be a work in progress as I try to find answers to various questions. I can’t fill the RotoGraphs article list with a new article every time I make a change or add more information (Ed. note: Sure you can, Jeff, we’ll post all of ’em!). Every few days or so, I’ll summarize the findings from the previous article’s work and keep moving forward. The series will come to an abrupt end if the framework exists for a start to the season since other analysis will then take priority.
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First off I hate that the season could be so short and it’s total B.S. that the players and owners are still negotiating a season. They should have started once the season was shutdown.

Also, I can understand if an owner or league just wants to sit out this season. This is especially true since other sports who have their sh…stuff together will be playing meaningful games soon.

With those two caveats out of the way, I am interested to see how a short season plays out since none of us have a playbook for it. The owners’ 48-game schedule is even more intriguing if Manfred decides to immediately implement it. The major impact for fantasy owners will be the games per week pending on where he sets the season start date. Here is how those 48-games could get divided up.

If it’s six games a week, that doesn’t change many player valuations. Anything less than that, it gets interesting. With around 5 or fewer games per week, everything will have a playoff feel. Aces will be thrown at every opportunity and suspect starters will have shorter leashes, if they’re starting at all.

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I’m cleaning up any news I have a backlog because I’m off on vacation next week and hopefully when I return, a decision will exist on an MLB season. As a reminder, the focus of this article is to dive deeper than the headline news like Chris Archer’s surgery.

General information

The effects of a concussion can still be felt two years later.

Interesting nugget on #concussions. Remember this when you have an athlete that suffered a concussion less than 2 years ago… pic.twitter.com/y70wfYiuPt

— Jesse Morse, MD (@DrJesseMorse) May 1, 2020

Here is a list of players who have been on the IL for a concussion over the past two years.
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In the final part of my latest injury investigation, I trying to see if pitchers who have accumulated a certain amount of injuries age worse than those who have stayed healthy. And if so, are there any rules-of-thumb that can be used. I’ve already examined chronically injured hitters and if accumulated days missed for pitchers lead to more Injured List (IL) trips. The results aren’t groundbreaking findings that constantly hurt pitchers declining faster at certain thresholds but now some numbers can be added to the narratives.

My overall goal is to see the accumulative effect of various injuries can lead to a pitcher aging faster. The factors I had never accounted for are accumulated IL days and times of the IL for elbow, shoulder, or arm injury. Also, I’m only diving into starters (GS/G >= .5) from 2010 to 2018 because relievers, especially closers, are already tough to project. I divided the starters by their age based on a steep production decline starting at age 29. For the pitcher’s talent level, I used ERA- that increase, like ERA, as a pitcher performs worse. The results were a little mixed.

One item to keep in mind, pitchers have historically, maintained their production, or declined as they age. While there is always the exception of a pitcher improving, most are headed down with the average change of 2.8 points of ERA- a year.

What I found from this data run and others not listed, age doesn’t matter. Also, while the average IL days steadily climb, the ERA- value jump seems to increase except when it doesn’t. I simplified the results and settled on a 120-day threshold with the following results.

Once a pitcher goes over the 120-day threshold (i.e. a full MLB season), their career declines at a faster than expected rate. Again, there are always going to expectations but rostering too many of these hurt starters increases the downside potential.

Now for one more angle that I had jotted in my to-do book. Most major pitcher injuries center around the arm, so I decided to focus just on them. I bucketed the information by the number of times a pitcher was on the IL for a general arm (e.g. forearm), elbow, or shoulder injury (no wrist or hand). With more than 99% of all instances in the single digits, a simple workable division was easy to find at 2 IL stints.

Even pitchers who had two or few IL stints weren’t in great shape with them averaging over 200 days on the IL. That third arm related IL trip can be a deal-breaker because the pitcher will, on average, will see their skill degrade about twice as fast as those with two or fewer trips.

And finally here are the pitchers who have over 120 days on the IL and three or more arm related IL stints (min 10 IP last season).

Several high ADP names fill the list like Morton, Darvish, Strasburg, Kershaw, and Cole. Does this information mean I won’t roster the pitcher? Maybe. With a fantasy team only starting nine pitchers, I’d like those pitchers to be as rock-solid as possible with little chance of decline. The downside means that I will need them to come with a discount and is an easy tiebreaker. That’s not helpful since that’s everyone’s injury take.

My stance on the information is wishy-washy because I am unsure. I haven’t fathomed a way to weight the information especially if I want to use it to create auction prices. I need to find a way to change ERA- to fantasy-relevant stats. It wouldn’t be that hard but I’m looking at two different inputs (total days and arm related trips). Also, I should incorporate possible time missed from previous IL trips. I’m going to let the information stew for a bit and unless I come to some divine revelation, I’ll perform a forced dive once this season is over or canceled.

I had no plans to write or investigate pitcher injuries again. I’ve done it several times in the past with similar results. Since I needed the same information to investigate if an often injured pitcher ages faster as I did with hitters, I had the data available so why not take another stab at projecting pitcher injury risks with a few different inputs.

For a refresher, here are some of my previous findings:

• Previous injuries, age, and workload matter.
• A low Zone% is a precursor to injuries
• High fastball velocity, not pitch type, leads to injuries.
• Shoulder and elbow injuries can linger for a while.

The small data difference is that instead of limiting the IL days to the previous one to three seasons, I’m just using the accumulated days. Also, I tracking the number of times the pitcher went on the IL for an arm, elbow, or shoulder injury. The two different factors are joined by fastball velocity, Zone%, and age to see what leads to injuries the next season.

I took all the data from all the pitchers and ran it through a Trees analysis and got the following chart.

This image sums up pitcher injuries perfectly. The best predictor of future injuries is past injuries. And just because a pitcher had never been on the IL, on average, they will still spend ~18 days on it. It’s just re-enforcing common sense backed up by study after study.

From my previous work, the injury rates between starters and relievers (i.e. starters who can’t stay healthy) are drastically different. For that reason, I ran the analysis splitting out starters (GS/G >= .5) from relievers (GS/G < .5). Here are the two decision trees.

Starters

Relievers

We have some further division taking place fastball velocity on both, a further out 460-day threshold for starters, and age requirement. I’m not a huge fan of the multi-branched tree with many variables. I’m all for keeping it simple. Using the above variables, I cut and diced the data into several possible combinations and came up with the following divisions.

Again, the rates are similar to my previous findings. The only changes are the pitch velocity groupings and that rough over-460 IL day group who average two months on the IL a year. For me, I focus on starters and will designate the starters into three risk groups:

• Low: No IL, low velo.
• Medium: No IL, high velo, and some IL, low velo.
• High: Some IL, high velo, and high IL.

Not all injuries can be avoided, but the injury downside is just another factor to consider when setting each pitcher’s fantasy value.

And what’s a study without the players to consider for the upcoming season. Here are the historic IL days and fastball velocity for any pitcher with 10 starts last season.

• The pitcher with the highest velocity and IL experience is Noah Syndergaard. That 2020 IL stint didn’t take long.
• The oldest starter to never have been on the IL is Tanner Roark at 33.
• Darvish and Morton are going as the 17th and 18th pitchers even though they’ve broken the 460-day threshold.
• Just go and scroll through the starters who have been on the IL and throw over 93-mph, especially over 95. Lots of them have spent considerable time on the IL over their careers. I’m thinking to target “safer” but elite starters if given the opportunity like Corbin, Bieber, Kershaw, Castillo, and Flaherty. There is no way to completely stay away from the injury risk but why not add a pitcher with a 28% chance (Boyd) than someone with a 63% chance (Ryu)

These conclusions were about 80% in line with what I expected with fastball velocity nudging itself in. Next up will be taking this information and seeing if a higher injury rate ages pitchers more than projected.

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