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On-Ball Value (OBV)

Expected Value ModelsLevel 3 — Advanced

Prerequisites

Expected Possession Value (EPV) ModelSARSA/RL Event Valuation

What It Is

A possession-state value model that assigns an OBV delta to every on-ball action by measuring its effect on both scoring probability AND conceding probability simultaneously. Unlike xG (shots only) or xT (zone-based), OBV values every action: passes, carries, dribbles, defensive actions, shots, and goalkeeper actions. Decomposes into sub-metrics: pass OBV, carry OBV, dribble OBV, defensive OBV, shot OBV, GK OBV — enabling position-appropriate player comparison.

Correct Execution

For each action: compute possession-state value before and after. ΔOBV = (P(scoring after) - P(conceding after)) - (P(scoring before) - P(conceding before)). Positive = the action improved the team's net position. Decompose by action type for player profiles.

Diagnostic Tree

Edges

🔑 Hidden Causal Lever

OBV Sub-Metric Decomposition Reveals Defensive Midfielders' Hidden Value

xg-modelson-ball-value-model →

DMs often show low total OBV because their contribution is reducing conceding probability (defensive OBV), not increasing scoring probability. A DM with -0.05 attacking OBV but +0.15 defensive OBV is net positive but looks negative on attacking sub-metrics alone.

What most people do
Report total OBV or attacking sub-metrics. Evaluate all midfielders on attacking-biased scales.
What the best do
Build position-specific OBV dashboards weighting sub-metrics by positional role. For DMs: defensive OBV is primary.
Why it's an edge: DMs are systematically undervalued because popular models emphasize attacking contribution. Correct defensive OBV valuation creates transfer arbitrage.
How to exploit: Build a "defensive value" leaderboard using defensive OBV. Cross-reference with market value. The biggest gaps are the arbitrage opportunities.
Hudl StatsBomb, 2025-01-27

Sources

  • Hudl StatsBomb, YouTube, 2025-01-27