Set Defense Detection from Event Data

A framework for identifying when a team is attacking against a set (organized) defense using only event data. Since no data feed labels "set defense" directly, four proxy thresholds are applied simultaneously to each event: (1) duration — event must be ≥20 seconds into the possession (defense has finished its transition), (2) pinballing — attacking team must control ≥80% of actions in the preceding window (not chaotic back-and-forth), (3) height — 3-event rolling average of ball distance from own goal must exceed the 60th percentile of center-back pass locations (~60m threshold), indicating attacking intent, (4) verticality — vertical speed must be <4.3 m/s (derived from the boundary between counter-attack and regular play distributions). When all four conditions are satisfied simultaneously, the event is classified as "attacking against a set defense."

Filter to attacking possessions that reach the final third (exclude set pieces — they introduce noise). For each event in qualifying possessions: check all four thresholds simultaneously. Events meeting all four = "true" (probing against set defense). Events failing one or more = "false" (transition moments, resets, or acceleration attempts). A possession against a set defense consists of alternating true and false blocks. Both matter: true blocks are the probing state; false blocks are the team's attempts to break the structure. Analyze both.

Key threshold derivations:

• 20-second duration: goal-scoring odds plateau after 20 seconds — this indicates the defense is fully set
• 80% ball control: less than 80% means the defending team is actively intervening (pinballing), not defending in shape
• Height (60th percentile of CB passing): if the ball is below this line, the attack hasn't committed forward
• Verticality (4.3 m/s): above this speed, the attack is a counter or fast break, not probing a set block

1. Including set pieces: Set piece possessions should be excluded — they introduce different tactical dynamics and noise into the set-defense analysis.
2. Only analyzing "true" events: The "false" blocks (acceleration attempts, resets, vertical passes) within set-defense possessions are where the team tries to break the block. Ignoring them misses the most tactically interesting moments.
3. Treating thresholds as universal: The 4.3 m/s verticality and 20-second duration thresholds are derived from specific league data. Different leagues may require different calibration.