Fantasy Value Above Replacement: Part One

This is the first part in a published four part series. If you’re interested in reading Part Two, Part Three, and the Update, click through!

In real-life baseball analysis, we have tools such as WAR to help us boil down a players’ contributions to a single number. Yet, in fantasy baseball, no such tool exists, sans a few “player raters” out there. The goal of this project was to create a number that would allow us to easily compare players’ values to each other in an effort to create accurate rankings before drafts begin. Today I will be rolling out a Fantasy Value Above Replacement metric, henceforth known as FVARz.

Using z-scores as the underpinning of this system can help keep things objective and accurate across the board. Simply start with a projected line in the players’ 5×5 categories and include it among the rest of the players at that position. Then, within each category, take the sum of the z-scores – the number of standard deviations away from the mean a player’s statistic is – and that determines the players’ value above the positional average. We then adjust for replacement level at that position, and you have a final number you can take to the bank. We can then use those overall value numbers to compare across positions, and even convert them into auction dollars.

For the sake of simplicity, all of these numbers are done for 12-team standard roto leagues, but the data can easily be manipulated to reflect a different number of teams, positional requirements, or player pools.

Step One: Comparing Inside the Position
Theory 1: Players can only play the positions that the game engine allows them, so those other players at their position are their only competition for a roster spot (sans UTIL).

All players’ raw numbers are compared only to those in their position grouping when it comes to overall value, because players can only play the position that the game engine allows. It does not make sense to directly compare Albert Pujols’ raw numbers to Robinson Cano’s raw numbers, for example, because they cannot occupy the same spot on your roster. Their raw data needs to be adjusted before we can directly compare them.

This is important because it is the way to calculate “position scarcity,” a key component in fantasy valuation. We can all agree that hitting 25 homers as a catcher is much more valuable than hitting 25 homers as an outfielder, and this will reflect that.

So compare the players’ numbers inside each position by using z-scores. Take the positional average and standard deviation in each 5×5 category, and calculate z-scores for each player’s performance in those 5×5 categories (we’ll talk more about how we properly do batting average and other rate stats later). We then just total up those z-scores, and call that out as our Fantasy Value Above Average, or FVAAz.

It is important to be consistent when deciding which players make it into your positional player pools. It is easiest to set an AB minimum (or IP for pitchers) and use it across the board in order to guarantee consistency. You can pick whatever number you like, but I’d recommend using a minimum around 400 AB’s.

Next, we’ll look at how we set our positional replacement levels, and why we do so.

Zach is the creator and co-author of RotoGraphs' Roto Riteup series, and RotoGraphs' second-longest tenured writer. You can follow him on twitter.

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11 years ago


that’s all i have.