State-Precision NAIL: No Forgetting
Last updated: 2026-08-24
This candidate tests a narrow question: does NAIL improve when its existing forward player prior is regularized according to each player's estimated uncertainty?
It is the first non-uniform State-Precision NAIL candidate. It received the same strict three-season frozen evaluation as production NAIL and is not promoted.
Contract
The player-prior mean remains the current NAIL v1.2.1.2 forward prior. Only the ridge precision changes by player.
After season \(t\), the RAPM fit supplies diagonal posterior variance \(P^+_{i,t}\). For the first candidate, no offseason variance is added:
The next fit rescales each player's prior penalty relative to the active season's median variance:
Higher-confidence estimates receive \(r_i>1\), while uncertain estimates receive \(r_i<1\). The published season lambda remains the global penalty scale.
This differs from production NAIL, which uses \(r_i=1\) for every player. It also differs from a decay experiment: this candidate is deliberately equivalent to \(\rho=1\), so it isolates uncertainty-aware regularization without offseason forgetting.
Promotion Gate
Run the existing three-season frozen evaluation. Compare it with NAIL v1.2.1.2 using the bootstrap confidence intervals already used for promotion decisions. Only if it clears that gate should we tune \(\rho<1\).
Frozen Result
The completed through-2025-26 artifact was replayed directly for 2023-24, 2024-25, and 2025-26. The replay uses each stored target prior vector and its matching prior-season context and schedule model; it does not retrain any seasons.
| Cohort | Model | Poss. RMSE | Eligible game RMSE | Full-game RMSE |
|---|---|---|---|---|
| Regular | v1.2.1.2 production | 1.197946 | 14.0107 | 14.2330 |
| Regular | State-Precision, no forgetting | 1.197970 | 14.0255 | 14.2783 |
| Playoffs | v1.2.1.2 production | 1.192710 | 16.6032 | -- |
| Playoffs | State-Precision, no forgetting | 1.192641 | 16.5191 | -- |
The small playoff improvement does not offset weaker regular-season possession, game, and team-level metrics. The candidate remains an evaluated, non-promoted row on the Three-Season Frozen Leaderboard.
Artifact:
artifacts/models/nail_state_precision_no_forgetting_frozen_backtest/frozen_multiseason_backtest/2023-24_to_2025-26/frozen_multiseason_backtest-2023-24-to-2025-26-20260825T043905Z-da55e4b8.