Brett Sullivan developed this statistic over at Project Prospect. The formula is (K%+.72*GB%-BB%)+(Age Level Standard-Actual Age)*7. Since the statistic is relatively simple, Sean P., who I write with over at Pending Pinstripes, came up with the idea to modify this into a hitting statistic.
After messing around for a while, we agreed on the following formula: (BB%+100*ISO+.74*LD%-K%)+(Speed Score-5)+(Age Level Standard-Actual Age)*7
I considered lowering the age multiplier, but the idea of this whole exercise is to give players who are younger than their competition credit for that. Also, line drive percentage is multiplied by .74 because approximately 74 percent of line drives turn into base hits. I multiplied ISO 100 times in order to put it on the same scale as the strikeout, walk, and line drive percentages.
I wanted to give batters some credit for their speed, so I chose to use FanGraphs' four component speed score. The average speed score is five, so we just chose to subtract that from the player's speed score to give them a few points if they are fast, or take away a few if they are slow. The age standards used are straight from Project Prospect:
A- (Staten Island and Charleston): 20
A+ (Tampa): 21
AA (Trenton): 22.5
AAA (Scranton/Wilkes-Barre): 24
The average ages for each league are higher than these numbers, but these provide a baseline of what age a prospect should be as they advance through a farm system.
I set the cutoff at 200 plate appearances at a given level. Jesus Montero didn't qualify for Tampa or Trenton, but I added him anyway. Of course, he ran away with the top two spots on the list.
Before getting to the list, let me start you off with a disclaimer. There are definitely quite a few flaws in this statistic. I'm not sure it provides us with any real meaning or predictive value; it's just an exercise that paints an interesting picture. The data I used is all from FanGraphs and First Inning. Okay, here is the list:
In case you were wondering, Jason Heyward had the highest score of any minor league batter: 66.56 in his Double-A stint. Jesus Montero didn't come out too far behind.
A few things jumped out at me when I was putting this list together. First and foremost, the Yankees' farm system really lacks power. Almost every single hitter on this list has an ISO below .120.
I like how this metric shows that while a guy like Neil Medchill put up good numbers, he really has to prove himself at a higher level before he should be taken seriously.
If I were to go back and revise my top 30 prospects list, I would definitely move Corban Joseph up a bit; he comes up as the fourth best hitter in the system according to this metric.
Even though Kevin Russo didn't get any age adjustments, he is still near the top of the list, further showing just how good his season was.
As I said earlier, I'm not sure how useful this statistic is. I plan on going back and taking a look at former Yankee prospects who graduated into successful big leaguers, and taking a look back at how this metric would have graded them. Until then, I have a newfound respect for Reegie Corona, Austin Jackson, and Corban Joseph.