Sunday, March 22, 2009

The Bo Jackson Theory Remix

Yesterday I posted the basis for the Bo Jackson Theory, which states that the future major league success of a power hitter is defined by plate discipline vs. IsoP vs. age. After posting my thoughts on the topic, I messed around with an Excel spreadsheet and came up with a rough numerical formula so that everyone can make their own charts and do their own slugger analysis and projections. It's not a perfect formula, but if you like numbers or are interested in player projections, it might be fun to play around with it. So, here it is.

The first part of the formula sets up a relationship between plate discipline and IsoP, with IsoP being weighted slightly more than K/BB Ratio.

IsoP *500 - (K%/BB% Ratio)*20

So, in the case of Albert Pujols, his minor league values (Isop = .229, K% = 9, BB% = 9) would result in the following formula values.

(.229)*500 - (9%/9%)*20 = 94.5

For now on this will be considered Value 1, which represents the basic influence of IsoP and K/BB Ratio.

So, now we need to account for age difference. After some cross analysis of players that played at the same minor league level over various years, I came up with some progression values to help eliminate the age difference problem.

Here's how it looks in the formula.

Value 1 + (Value 1 * 10%) * (24 - Age at AA Ball)

Essentially, if a player played AA ball at the age of 24, their power score is equal to Value 1. If they played AA ball at the age of 23, they get an adjustment of 10% to account for the age difference. Likewise, if a player was 22 at AA, they get a 20% boost (10% * 2 years), if they're 21 at AA they get an extra 30%, and so on and so on. In basic terms, for every year younger that a player plays at AA ball before the age of 24, they get a 10% increase in their Value 1 score.

So, if we apply that to Albert Pujols, we get the following.

94.5 + (94.5 * 10%) * (24 - 21) = 122.85

Pujols actually never played at AA ball, but he played very well at A ball as a 20 year old, so we would assume that had the Cardinals assigned him to AA ball, they would have done so when he was 21 years old.

Ok, now we have accounted for plate discipline, IsoP, and finally age, and
if we apply the formula to enough players, we can create a huge chart of past or current major league players with various scores, and then determine where minor league prospects fit in. For example, here is a short list of about 20 players, with their individual Bo Jackson Theory Power Score (for now on, I'll just refer to it as their "BoJa" score).

We could debate as to exactly how accurate the BoJa score is, but I think in general it gets about as accurate as we can expect from a basic model of just 3 factors and some very simple math (by the way, Jackson scored a 25 in this model). We must keep in mind that the score is only a power ranking system, and does not account for other skills. Guys like Tony Gwynn would probably not score well at all using the BoJa model, but it doesn't mean he (or players like him) were and are not great hitters. However, for players like Bo Jackson who relied on their power above all other skills, this scoring system may be very helpful in evaluating future major league success.

If anyone is interested in having their own BoJa scoring system in an Excel file, let me know, and I'll e-mail you the one I've created. You can mess with the numbers and values in the formula and try to improve on the accuracy of the BoJa system, or just use it to quickly evaluate player power potential.

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