NAIL-RAPM v1.2.4: Free-Throw Replacement
NAIL-RAPM v1.2.4 tests the conditional-credit hypothesis exposed by
v1.2.3: replace additive
usage_per_100 with additive free_throw_attempts_per_100 rather than
including both. This is a strict sibling of v1.2.1 with eight additive player
profile coordinates and the same two retained non-additive lineup terms.
All other contracts are unchanged: value-conditioned aging, exposure-gated cold starts, gap-returner bridging, forward-safe stat-specific padding, and the Ridge lineup fit.
Contract
For a unit (U), v1.2.4 replaces
with
The retained non-additive terms remain top_two_assists and
usage_concentration. Thus this tests the additive offensive-load coordinate,
not whether distribution of usage within a unit matters.
Decision Rule
Fit recursively through 2025-26, evaluate frozen 2023-24 through 2025-26 regular seasons and playoffs against v1.2.1, then run a paired 2,000-draw game-stratified bootstrap. Promotion requires a competitive primary full-game-margin result, not merely a permissive no-material-harm gate.
The coefficient audit includes binary sign share and directional mass,
so a small sign crossing does not outweigh a persistently material direction.
Frozen Result
v1.2.4 does not promote the FTA/100 replacement. It makes the isolated possession-MAE result better, but the primary regular-season margin metrics remain worse than v1.2.1.
| Metric | v1.2.1 | v1.2.4 | Difference (v1.2.4 - v1.2.1) |
|---|---|---|---|
| Regular possession RMSE | 1.197952 | 1.197966 | +0.000014 |
| Regular possession MAE | 1.141355 | 1.141328 | -0.000027 |
| Regular eligible game RMSE | 14.0245 | 14.0457 | +0.0211 |
| Regular full-game RMSE | 14.2521 | 14.2733 | +0.0212 |
| Game-winner accuracy | 68.24% | 68.19% | -0.06 pp |
| Team NetRtg RMSE | 3.2706 | 3.2933 | +0.0226 |
| Pythagorean-win RMSE | 7.0351 | 7.0459 | +0.0108 |
| Playoff possession RMSE | 1.192709 | 1.192706 | -0.000003 |
| Playoff eligible game RMSE | 16.5942 | 16.5988 | +0.0046 |
The paired 2,000-draw bootstrap estimates pooled full-game RMSE at +0.0212
for v1.2.4 relative to v1.2.1, with 95% interval [-0.0025, +0.0433]; the
challenger is better in 3.5% of draws. It passes the permissive no-material-harm
safety gate but fails to provide a reason to displace v1.2.1.
Profile Coefficients
Removing additive Usage/100 resolves the conditional collinearity seen in
v1.2.3. FTA/100 is positive in 28 of 29 source seasons, has median
standardized coefficient +1.360, and carries 99.96% positive directional
mass over the full history (100% across the latest ten seasons). This is a
credible coordinate, but its predictive contribution is redundant after the
remaining profile contract.
Retained Non-Additive Coefficients
The two retained non-additive lineup terms do not change under this replacement experiment.
The fit, frozen replay, bootstrap, and directional-mass ledger are persisted
under artifacts/models/forward_nail_rapm_v124_free_throw_replacement,
artifacts/models/nail_v124_free_throw_replacement_frozen_backtest,
artifacts/models/nail_v124_free_throw_replacement_bootstrap, and
artifacts/models/analysis/nail_v124_free_throw_replacement_weight_audit.