diff --git a/src/services/adapters/statcastAdapter.js b/src/services/adapters/statcastAdapter.js
index c3d6bba..762372f 100644
--- a/src/services/adapters/statcastAdapter.js
+++ b/src/services/adapters/statcastAdapter.js
@@ -66,6 +66,12 @@ const FEEDS = Object.freeze({
   // carries only each pitcher's primary pitch, which left velo at 53% coverage
   // and unusable as an archetype axis.
   pitch_velo: (y) => `${BASE}/pitch-arsenals?year=${y}&min=1&type=avg_speed&hand=&csv=true`,
+  // FIELDING — Outs Above Average, per fielder, with his team. Free, same host,
+  // no key. This is the ONLY defence signal available to us: nothing in the
+  // other six feeds measures fielding at all, and the obvious substitutes
+  // (a team's pitchers' hits-allowed) conflate pitching WITH defence and would
+  // validate the wrong skill. Measured live 2026-08-03: 513 fielders.
+  fielding_oaa: (y) => `${BASE}/leaderboard/outs_above_average?type=Fielder&startYear=${y}&endYear=${y}&split=no&team=&range=year&min=1&pos=&roles=&viz=hide&csv=true`,
 });
 
 /** statsapi — free, no key. Two calls that complete the Tier-A joins.
@@ -285,10 +291,11 @@ async function fetchSeason(season = DEFAULT_SEASON, opts = {}) {
     }
   };
 
-  const [bd, bbb, pd, pbb, mv, ars, velo] = await Promise.all([
+  const [bd, bbb, pd, pbb, mv, ars, velo, oaa] = await Promise.all([
     get('batter_discipline'), get('batter_batted_ball'),
     get('pitcher_discipline'), get('pitcher_batted_ball'),
     get('pitch_movement'), get('pitch_arsenal'), get('pitch_velo'),
+    get('fielding_oaa'),
   ]);
   const [hands, roles] = await Promise.all([fetchHandedness(season, opts), fetchRoles(season, opts)]);
 
@@ -301,15 +308,78 @@ async function fetchSeason(season = DEFAULT_SEASON, opts = {}) {
     pitchMix: indexArsenal(ars, indexPitchMix(mv), indexVelo(velo)),
     handedness: hands,
     roles,
+    fielding: indexFielding(oaa),
+    teamDefense: aggregateTeamDefense(oaa),
     counts: {
       batter_discipline: bd.length, batter_batted_ball: bbb.length,
       pitcher_discipline: pd.length, pitcher_batted_ball: pbb.length,
       pitch_movement: mv.length, pitch_arsenal: ars.length, pitch_velo: velo.length,
-      handedness: hands.size, pitcher_roles: roles.size,
+      handedness: hands.size, pitcher_roles: roles.size, fielding_oaa: oaa.length,
     },
   };
 }
 
+/**
+ * Per-fielder OAA → Map(mlbam id → { oaa, runs_prevented, success_diff, pos }).
+ *
+ * UNKNOWN IS NOT ZERO, and it bites unusually hard here: an OAA of 0 is a REAL
+ * measurement meaning "exactly average", while a missing row means we have no
+ * read on that fielder. Coercing absence to 0 would silently assert that every
+ * unmeasured fielder is league-average — the single most common defensive
+ * profile — which is a fabricated fact, not a neutral default.
+ */
+function indexFielding(rows) {
+  const out = new Map();
+  for (const r of rows || []) {
+    const id = numOrNull(r.player_id);
+    if (id == null) continue;
+    out.set(Number(id), {
+      oaa: numOrNull(r.outs_above_average),
+      runs_prevented: numOrNull(r.fielding_runs_prevented),
+      // "-4%" → -4. The success-rate columns arrive percent-formatted.
+      success_diff: numOrNull(String(r.diff_success_rate_formatted || '').replace('%', '')),
+      pos: r.primary_pos_formatted || null,
+      team: r.display_team_name || null,
+    });
+  }
+  return out;
+}
+
+/**
+ * TEAM defence → Map(team nickname → { oaa_sum, oaa_mean, success_diff_mean, fielders }).
+ *
+ * A batter's prop is conditioned on the DEFENCE BEHIND THE PITCHER HE FACES, so
+ * team level is the unit that matters. Summed OAA is the team's total outs
+ * converted above average; the mean is carried too because a team with more
+ * measured fielders would otherwise look better merely for being measured more.
+ * A team with no measured fielders is ABSENT, never 0.
+ */
+function aggregateTeamDefense(rows) {
+  const acc = new Map();
+  for (const r of rows || []) {
+    const team = r.display_team_name;
+    const oaa = numOrNull(r.outs_above_average);
+    if (!team || oaa == null) continue;
+    const cur = acc.get(team) || { oaa_sum: 0, fielders: 0, diff_sum: 0, diff_n: 0 };
+    cur.oaa_sum += oaa;
+    cur.fielders += 1;
+    const d = numOrNull(String(r.diff_success_rate_formatted || '').replace('%', ''));
+    if (d != null) { cur.diff_sum += d; cur.diff_n += 1; }
+    acc.set(team, cur);
+  }
+  const out = new Map();
+  for (const [team, v] of acc) {
+    if (v.fielders < 3) continue;         // too thin to call a team defence
+    out.set(team, {
+      oaa_sum: v.oaa_sum,
+      oaa_mean: v.oaa_sum / v.fielders,
+      success_diff_mean: v.diff_n > 0 ? v.diff_sum / v.diff_n : null,
+      fielders: v.fielders,
+    });
+  }
+  return out;
+}
+
 /** statsapi handedness → Map(id → {bats, throws, position}). ONE call, and it
  *  carried 1,316/1,316 in the live probe. */
 async function fetchHandedness(season, opts = {}) {
@@ -357,6 +427,7 @@ async function fetchJson(url, opts = {}) {
 
 module.exports = {
   fetchSeason,
+  indexFielding, aggregateTeamDefense,
   DEFAULT_SEASON,
   FEEDS,
   __internals: {
diff --git a/src/services/statcastAggregateService.js b/src/services/statcastAggregateService.js
index 9b84727..30a36a5 100644
--- a/src/services/statcastAggregateService.js
+++ b/src/services/statcastAggregateService.js
@@ -255,6 +255,32 @@ async function refreshSeason(opts = {}) {
     summary.written += batch.length;
   }
 
+  // ── TEAM DEFENCE ──────────────────────────────────────────────────────
+  // Written DATED, so point-in-time is available the first time it is needed
+  // rather than retrofitted after a wrong answer (the statcast_aggregates
+  // lesson). Best-effort like every other side-write: a defence failure must
+  // never fail the mechanism refresh.
+  try {
+    const td = feeds.teamDefense;
+    const asOfD = (opts.asOfDate || started).slice(0, 10);
+    if (td && td.size > 0) {
+      const rows = [...td.entries()].map(([team, v]) => ({
+        as_of_date: asOfD, sport, season, team,
+        oaa_sum: v.oaa_sum, oaa_mean: v.oaa_mean,
+        success_diff_mean: v.success_diff_mean, fielders: v.fielders,
+        source: 'statcast_oaa',
+      }));
+      const { error } = await sb.from('team_defense')
+        .upsert(rows, { onConflict: 'as_of_date,sport,season,team' });
+      if (error) summary.team_defense_error = error.message;
+      else summary.team_defense_written = rows.length;
+    } else {
+      summary.team_defense_written = 0;
+    }
+  } catch (e) {
+    summary.team_defense_error = e.message;
+  }
+
   // ── POINT-IN-TIME RETENTION ───────────────────────────────────────────
   // `statcast_aggregates` is upserted in place, so it holds exactly ONE as-of
   // date and every prior version is destroyed. That silently makes any backtest