Expected Runs = your home runs + your other times-on-base scoring at the league rate, scaled by how well your team brings runners home. Expected RBI = your total bases × the league RBI-per-TB rate, scaled by how many runners hit ahead of you (team OBP).

Earned vs lucky: runs split into what the hitter controls — times on base (H + BB + HBP) — and what he doesn’t — R/TOB, how often those baserunners actually scored. A high R/TOB means the lineup is bringing him home at a fortunate clip (regression risk); a low R/TOB with lots of TOB means the runs are coming even without help (real, sticky). RBI break down the same way into total bases (his power) × RBI/TB (runners-on luck).

Opportunity-proxy model — it uses on-base, total-bases and team run-environment rather than play-by-play base states, so the residual captures the timing luck that historically regresses. Every input traces to real season totals; coefficients are computed from this season’s league, not hardcoded.