Athleticism Metric: Setting the Ground Work

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.

Compiling this information even a few years ago would have included more guesstimating but the available StatCast data simplifies the process. The first two factors, power and speed, are easy to measure using max exit velocity and sprint speed. Agility and quickness are a little tougher to nail down, but I settled on the defensive component of WAR.

The data is/are far from perfect. The first adjustment I made was to remove the pitch-framing element from catchers. I kept all the other elements including the positional and fielding adjustment. If a player can only play first base (one hit to his athleticism), he better do a great job of it. Additionally, I adjusted the fielding value to a per-game rate so all hitters are on a level playing surface since defensive WAR is effectively a counting stat.

I did consider adding a couple of factors. One was height. I read up on the ideal height for any athlete and there seems to be a link between height and injury. I hoping to use height, but in the next step. It’s going to be one of several factors.

The other input that I’m still unsettled on is a hitter’s ability to swing a bat and make contact (Contact%). After a few private debates, I think this trait falls more in the hand-eye coordination basket. I can be talked into being wrong and flip-flop on my decision.

So to get my athletic value, I took all the hitters from the past five seasons (length of available StatCast data) with a minimum of 200 PA and calculated the z-score for the three traits. I weighted each trait evenly for now. And again, I could be talked into weighing one trait more or less than the others.

For a final value, I add the three values together. At some later date, I might set these values on a 100 scale (with 100 is league average) or possibly the 20-80 scouting scale. I’ll nail down the formula first before moving on.

It’s time to start doing the idiot check. Here are the top-10 players from the past two seasons (full list).

The two names that seem out of place are Stanton and Judge. Both are highly rated based on three traits. These two examples are why I want to jump ahead to include height showing how big bodies breakdown. I just need to tap the breaks and get athleticism down first.

Here are the bottom ten from the two seasons (worst is listed first).

While not a household name, Tony Kemp seems out of place. Just digging into his inputs, he has almost no power with average to below-average speed and defense. Maybe Kemp is the type of player this process is hoping to find.

So readers, what seems off? Please scrutinize the full list and nitpick everything. I’ll remain active in the comments and can quickly create new rankings if needed for comparison. Once I get athleticism done, I can then start investigating if athletic hitters age better or not.