Joe Wilkey member 2 years ago

While the z-score method is a potentially good way to evaluate players for fantasy purposes, this is not a particularly good way to go about it, for several reasons.

First, while there should probably be a PA cutoff so the means/SDs aren’t skewed by the numerous players with a small number of PA, you should definitely include more than just the number of players to fill out the starting spots. Steamer WAR is almost certainly not a good place to start, since SB are relatively meaningless in the WAR calculation, but fairly valuable in a fantasy setting, and defense is accounted for in the WAR calculation, which literally has zero value in the vast majority of fantasy leagues. For this example, if you include Tim Anderson (13th best Steamer WAR) instead of O’Neill Cruz in this example, Corey Seager is now the replacement level SS and everyone’s overall z-score drops by 7 points.

Second, as others have stated, calculating z-scores for just a single position is not the best choice, since a HR from a catcher counts just as much as a HR from a 1B. The entire player population (defined by whichever playing time cutoff you decide) should be used to calculate the means/SDs.

Third, the replacement player is not the last player to fill lineups, it is the next player, since that is theoretically the player you can pick up for free. The argument could be made that it’s actually lower than that, since some players could theoretically be drafted and kept on the bench the entire season. In conjunction with that, the replacement player should be defined as a $1 player, not a $0 player, since you can’t own a player without spending $1 on them.

Fourth, there is no explanation on what goes into the dollar values. It looks like you simply summed the z-scores after the replacement adjustment. There is a simple equation for calculating dollar values from the replacement adjusted z-scores: (team salary – roster spots)*(# of teams in league)*(player adjusted z-score)/(total adjusted z-score of all above replacement players) + 1. This is the core principal of this method.

I hate to be such a downer, and I’m aware that the article refers to the book, but a lot of what is presented is not best practices, and it could lead people down the wrong path.