diff --git a/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsIndices.java b/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsIndices.java
index 835e724b99850..95dad715c762d 100644
--- a/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsIndices.java
+++ b/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsIndices.java
@@ -81,7 +81,7 @@ public ClusterStatsIndices(List<ClusterStatsNodeResponse> nodeResponses, Mapping
 
         for (ClusterStatsNodeResponse r : nodeResponses) {
 
-            r.getNodeIndexShardStats().indexCountMap.forEach(
+            r.getNodeIndexShardStats().indexStatsMap.forEach(
                 (index, indexCountStats) -> countsPerIndex.merge(index, indexCountStats, (v1, v2) -> {
                     v1.addStatsFrom(v2);
                     return v1;
diff --git a/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodeResponse.java b/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodeResponse.java
index 60296e8732f3b..6a58c916f8027 100644
--- a/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodeResponse.java
+++ b/server/src/main/java/org/opensearch/action/admin/cluster/stats/ClusterStatsNodeResponse.java
@@ -32,6 +32,7 @@
 
 package org.opensearch.action.admin.cluster.stats;
 
+import org.opensearch.Version;
 import org.opensearch.action.admin.cluster.node.info.NodeInfo;
 import org.opensearch.action.admin.cluster.node.stats.NodeStats;
 import org.opensearch.action.admin.indices.stats.ShardStats;
@@ -65,8 +66,13 @@ public ClusterStatsNodeResponse(StreamInput in) throws IOException {
         }
         this.nodeInfo = new NodeInfo(in);
         this.nodeStats = new NodeStats(in);
-        shardsStats = in.readArray(ShardStats::new, ShardStats[]::new);
-        this.nodeIndexShardStats = new NodeIndexShardStats(in);
+        if (in.getVersion().onOrAfter(Version.V_2_13_0)) {
+            this.nodeIndexShardStats = new NodeIndexShardStats(in);
+            shardsStats = null;
+        } else {
+            shardsStats = in.readArray(ShardStats::new, ShardStats[]::new);
+            nodeIndexShardStats = null;
+        }
     }
 
     public ClusterStatsNodeResponse(
@@ -123,7 +129,10 @@ public void writeTo(StreamOutput out) throws IOException {
         }
         nodeInfo.writeTo(out);
         nodeStats.writeTo(out);
-        out.writeArray(shardsStats);
-        nodeIndexShardStats.writeTo(out);
+        if (out.getVersion().onOrAfter(Version.V_2_13_0)) {
+            nodeIndexShardStats.writeTo(out);
+        } else {
+            out.writeArray(shardsStats);
+        }
     }
 }
diff --git a/server/src/main/java/org/opensearch/action/admin/cluster/stats/NodeIndexShardStats.java b/server/src/main/java/org/opensearch/action/admin/cluster/stats/NodeIndexShardStats.java
index e8a9990c41c99..2e364a97fa551 100644
--- a/server/src/main/java/org/opensearch/action/admin/cluster/stats/NodeIndexShardStats.java
+++ b/server/src/main/java/org/opensearch/action/admin/cluster/stats/NodeIndexShardStats.java
@@ -12,7 +12,6 @@
 import org.opensearch.action.admin.indices.stats.ShardStats;
 import org.opensearch.action.support.nodes.BaseNodeResponse;
 import org.opensearch.cluster.node.DiscoveryNode;
-import org.opensearch.common.Nullable;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.core.common.io.stream.StreamOutput;
 import org.opensearch.index.cache.query.QueryCacheStats;
@@ -26,6 +25,9 @@
 import java.util.HashMap;
 import java.util.Map;
 
+/**
+ * Node level statistics used for ClusterStatsIndices for _cluster/stats call.
+ */
 public class NodeIndexShardStats extends BaseNodeResponse {
 
     DocsStats docs;
@@ -34,7 +36,7 @@ public class NodeIndexShardStats extends BaseNodeResponse {
     QueryCacheStats queryCache;
     CompletionStats completion;
     SegmentsStats segments;
-    Map<String, ClusterStatsIndices.ShardStats> indexCountMap;
+    Map<String, ClusterStatsIndices.ShardStats> indexStatsMap;
 
     protected NodeIndexShardStats(StreamInput in) throws IOException {
         super(in);
@@ -44,7 +46,7 @@ protected NodeIndexShardStats(StreamInput in) throws IOException {
         queryCache = in.readOptionalWriteable(QueryCacheStats::new);
         completion = in.readOptionalWriteable(CompletionStats::new);
         segments = in.readOptionalWriteable(SegmentsStats::new);
-        indexCountMap = in.readMap(StreamInput::readString, ClusterStatsIndices.ShardStats::new);
+        indexStatsMap = in.readMap(StreamInput::readString, ClusterStatsIndices.ShardStats::new);
     }
 
     protected NodeIndexShardStats(DiscoveryNode node, ShardStats[] indexShardsStats) {
@@ -56,14 +58,14 @@ protected NodeIndexShardStats(DiscoveryNode node, ShardStats[] indexShardsStats)
         this.queryCache = new QueryCacheStats();
         this.completion = new CompletionStats();
         this.segments = new SegmentsStats();
-        this.indexCountMap = new HashMap<>();
+        this.indexStatsMap = new HashMap<>();
 
         // Index Level Stats
         for (org.opensearch.action.admin.indices.stats.ShardStats shardStats : indexShardsStats) {
-            ClusterStatsIndices.ShardStats indexShardStats = this.indexCountMap.get(shardStats.getShardRouting().getIndexName());
+            ClusterStatsIndices.ShardStats indexShardStats = this.indexStatsMap.get(shardStats.getShardRouting().getIndexName());
             if (indexShardStats == null) {
                 indexShardStats = new ClusterStatsIndices.ShardStats();
-                this.indexCountMap.put(shardStats.getShardRouting().getIndexName(), indexShardStats);
+                this.indexStatsMap.put(shardStats.getShardRouting().getIndexName(), indexShardStats);
             }
 
             indexShardStats.total++;
@@ -92,6 +94,6 @@ public void writeTo(StreamOutput out) throws IOException {
         out.writeOptionalWriteable(queryCache);
         out.writeOptionalWriteable(completion);
         out.writeOptionalWriteable(segments);
-        out.writeMap(indexCountMap, StreamOutput::writeString, (stream, stats) -> stats.writeTo(stream));
+        out.writeMap(indexStatsMap, StreamOutput::writeString, (stream, stats) -> stats.writeTo(stream));
     }
 }