• 4.1 baseline — 0.6 × season 4.3 (4 gm) + 0.4 × last 5 3.8
• −0.2 opponent leak — they concede 88.8/game vs a 93.4 league average

Derived, not measured — plain arithmetic over his real games, shown in full. Adjustments can overlap (a game at this ground can also be a wet one); they add simply, and this note is the admission.