Value-based drafting is a popular approach for achieving an optimal draft. Essentially, the strategy tries to maximize the value of your team vs. your opponents’ teams. Instead of just drafting “the best available player” in each round (based on total projected fantasy points), the value-based approach suggests that you grab the player that offers the most incremental value in relation to the likely rosters of your opponents. The scarcer a position is, the more likely you’ll have an advantage over your opponents by grabbing a strong player at that position.
VORP and VONA are two variations of value-based drafting and are summarized below. A great overview of VORP and VONA can also be found at Advanced NFL Stats.
VORP (Value Over Replacement Player)
VORP was made popular by the statistical nuts that analyze MLB players. VORP measures player values by looking at each player’s contribution when compared to a readily available “replacement player” that the team could pick up.
For fantasy football, we’ve modified this concept a bit by looking at each player’s value over a readily available player on the waiver wire from the same position. We predict the number of players at each position that will be drafted by your league (based on # of teams, roster requirements, and our pick prediction algorithm), and then we take each player’s projected fantasy points and compare it to the player you could easily replace him with on the waiver wire.
The difference in fantasy points between the players is the VORP. For simplicity, we assume a VORP of zero for any player that has negative value (since you can easily drop him for the player on the waiver wire).
VONA (Value Over Next Available)
The strategy of “dynamic” value-based drafting bakes in a forecast of the number of players at each position that will be taken between your current pick and your next pick. It assigns values to your current options by assessing how much better those options are compared to what will be available to you at your next pick. An extreme example is when a player will still be available to you in the following round. That means his VONA (value over next available) is zero because a player with the same value (in this case, the very same player) will be an option for you with your next pick.
Theoretically, VONA is a great strategy to use. Practically speaking, it’s very difficult to do on your own in a draft. This is because you need to predict whom your opponents will take between your picks, and calculate the incremental fantasy points you’ll achieve for each option available... all in less than 60 seconds.
The good news is that our algorithm does all this predicting and math for you. Please note that the number of picks between rounds impacts VONA. If you’re drafting in the 12th spot of a 12-team league, your VONA for all players will naturally be zero on the first of your two back-to-back picks.
VOLS (Value Over Last Starter)
VOLS measures the difference in fantasy points between the player you are about to pick and the worst player at the same position who will end up as a starter for one of your opponents. For simplicity, we assume a VOLS of zero for any player that has negative value.
VBD Score (Value Based Drafting Score)
VBD score aggregates VORP, VONA and VOLS into one single number. It allows you to conveniently compare players.