Prospect Scouting & Stats — Hitter Power

First of all, thanks to everyone who commented and suggested an idea or multiple ideas for myself and my fellow RotoGraphers to write about as we sit here impatiently hoping and waiting for baseball to begin. Unfortunately, the vast majority either required data that would be impossible for me to collect or would require the type of analysis that’s way above my abilities. However, I did come away with one idea that I’m going to run with at some point in the future. Before I do that, a comment actually led me to checking out our THE BOARD: Scouting + Stats!, which reminded me how freakin’ awesome it is.

Since I’m not much of a prospect guy, I admittedly don’t regularly peruse THE BOARD or even read prospect articles. But seeing the scouting grades meshed with the stats (and even the inclusion of EV and Max EV for hitters!!!) got me excited. So for the next couple of weeks, I’m going to focus on writing different articles relating to prospect scouting grades and stats. I’ll review leaderboards in different scouting grades, calculate various correlations, and we’ll get to know our top prospects a bit better. As always, if you want me to look at something relating to THE BOARD, prospect scouting and stats, let me know!

I decided to start by calculating the correlations between the various power-related scouting grades and a couple of stats to minor league HR/FB rate and ISO. I began by downloading all the prospects on THE BOARD that were slapped with scouting grades, and then pulled in their HR/FB rates and ISO marks. After removing players with missing data, my correlation population ranged between 319 and 346 players.

Now, for the correlations…

Except for Pull%, which I decided to throw in there just for the heck of it, and Game Power – Future, we find that every metric correlates better with HR/FB rate than ISO. That’s interesting, and probably because when we grade power, we don’t really consider triples a result of big power. Power really means home runs. So this is a good thing, because fantasy players mostly just care about a hitter’s home run potential, with doubles potential mattering significantly less.

Unsurprisingly, we find that the correlations with HR/FB rate are higher for the Present grades versus the Future grades. This obviously makes sense, as the Present is a hitter’s current talent, while the Future is a projection. What is surprising to me is that the Raw Power grades are actually higher than the Game Power grades! I think of Raw Power as a kind of batting practice power, while Game Power is how much of that batting practice power the hitter actually carries over into games. So you would expect Game Power to correlate better with the actual measure of home run ability in games, HR/FB rate, but it didn’t. Perhaps it’s a sample size issue. Whatever the reason, it means that you shouldn’t place a much heavier weight on the Game Power grade and instead give both grades equal weight.

I had no idea we had exit velocity (EV) marks for minor leaguers. While I don’t use exit velocity in my xHR/FB rate equation, and fly ball EV would be far more valuable than overall EV, any EV for minor leaguers is better than none. Amazingly, average EV tied with Max EV for the highest correlation with HR/FB rate. That’s awesome! Now I wonder — do we find a higher correlation with HR/FB rate if the Present Game/Raw Power scouting grades agree with the EV? I’ll have to look into that for a future post (Thursday’s?).

Sadly, Pull%, while not completely meaningless, doesn’t tell us a whole lot about a prospect’s power. Like EV, it would have been more valuable to have fly ball pull rate, which is a component of my xHR/FB rate equation, but overall pull rate incorporates too much data we don’t want. A batter could have a high Pull%, but it’s driven by a high pull grounder rate, rather than fly ball rate, and we don’t care what the hitter does on his grounders.

So that’s a wrap on correlations with prospect power metrics, merging scouting and stats. I hope you have your prospect hat on, because that’s all I’ll be posting about for a while!