Some interesting nuances introduced yesterday with respect to the way we calculate zone starts by @arikparknass. The same points were made in this piece by @hockeyanalysis which was posted a few weeks ago.
The point made was that we should only be counting faceoffs for individual skaters when they were off the ice prior to the draw. Why? Because any faceoff that occurs afterwards is influenced by the possession game of the player of interest. Poor possession players are more likely to be in their own end and have their goaltender cover the puck. They then remain on the ice for the ensuing faceoff and their OZS% decreases. Zone starts, the way they are calculated at the moment, are NOT independent from possession.
In light of all of this, I will be offering usage adjusted possession numbers that do not adjust for zone starts in addition to the usage adjusted metrics already available here at OwnThePuck. The R^2 between U.A. Corsi% (-ZS) and U.A. Corsi% (+ZS) is 0.9239 (400+ min).