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Over at Footballguys.com, I build upon Joe Bryant’s VBD and create the idea of Expected VBD. While VBD is a great way to understand the value of players, Expected VBD explains how we draft. This concept is why even though you may expect some kickers and fantasy defenses to perform well, you don’t take them early in the draft because they have low Expected VBDs. So what is Expected VBD?
Instead of drafting according to strict VBD, you should be drafting to something I’ll call Expected VBD, which is best defined by an example. Suppose Russell Wilson has three equally possible outcomes this year: he has a one-in-three chance of scoring 425 fantasy points, 325 fantasy points, and 225 fantasy points. Further, let’s assume that the baseline number of fantasy points at the quarterback position is 300 fantasy points.
We would project Wilson to score 325 points, which would be the weighted average of his possible outcomes. This means VBD would tell you that he is worth 25 points, because 325 is 25 points above the baseline. Expected VBD works like this: If Wilson scores 425 points, he’ll produce 125 points of VBD. If he scores only 325 points, he’ll be worth +25, and if he scores only 225 points, he’s going to have -125 points of VBD. In real life, players with negative VBD scores can be released or put on your bench. So if Wilson scores 225 points (probably due to injury), you’ll start another quarterback, roughly a quarterback who can give you baseline production.
So when Wilson scores 225 fantasy points, his VBD is 0, not -75. That means his Expected VBD would be (125+25+0)/3, or 50. Wilson’s VBD according to our projections may be only 25, but his Expected VBD is twice as large because Expected VBD does not provide an extra penalty for sub-baseline performances. Not surprisingly, different positions have different amounts of Expected VBD associated with them.
Below is the summary graph — it has quickly become one of my all-time favorite graphs — which shows the Expected VBD by each position according to Average Draft Position.
I go into much more detail in the full article.