diff --git a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequest.java b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequest.java
index 2b796b08f9c..08c188ae998 100644
--- a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequest.java
+++ b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequest.java
@@ -21,13 +21,11 @@ package org.elasticsearch.action.explain;
 
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ValidateActions;
-import org.elasticsearch.action.support.QuerySourceBuilder;
 import org.elasticsearch.action.support.single.shard.SingleShardRequest;
-import org.elasticsearch.client.Requests;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.search.fetch.source.FetchSourceContext;
 
 import java.io.IOException;
@@ -41,7 +39,7 @@ public class ExplainRequest extends SingleShardRequest<ExplainRequest> {
     private String id;
     private String routing;
     private String preference;
-    private BytesReference source;
+    private QueryBuilder<?> query;
     private String[] fields;
     private FetchSourceContext fetchSourceContext;
 
@@ -102,17 +100,12 @@ public class ExplainRequest extends SingleShardRequest<ExplainRequest> {
         return this;
     }
 
-    public BytesReference source() {
-        return source;
+    public QueryBuilder<?> query() {
+        return query;
     }
 
-    public ExplainRequest source(QuerySourceBuilder sourceBuilder) {
-        this.source = sourceBuilder.buildAsBytes(Requests.CONTENT_TYPE);
-        return this;
-    }
-
-    public ExplainRequest source(BytesReference source) {
-        this.source = source;
+    public ExplainRequest query(QueryBuilder<?> query) {
+        this.query = query;
         return this;
     }
 
@@ -159,8 +152,8 @@ public class ExplainRequest extends SingleShardRequest<ExplainRequest> {
         if (id == null) {
             validationException = ValidateActions.addValidationError("id is missing", validationException);
         }
-        if (source == null) {
-            validationException = ValidateActions.addValidationError("source is missing", validationException);
+        if (query == null) {
+            validationException = ValidateActions.addValidationError("query is missing", validationException);
         }
         return validationException;
     }
@@ -172,7 +165,7 @@ public class ExplainRequest extends SingleShardRequest<ExplainRequest> {
         id = in.readString();
         routing = in.readOptionalString();
         preference = in.readOptionalString();
-        source = in.readBytesReference();
+        query = in.readQuery();
         filteringAlias = in.readStringArray();
         if (in.readBoolean()) {
             fields = in.readStringArray();
@@ -189,7 +182,7 @@ public class ExplainRequest extends SingleShardRequest<ExplainRequest> {
         out.writeString(id);
         out.writeOptionalString(routing);
         out.writeOptionalString(preference);
-        out.writeBytesReference(source);
+        out.writeQuery(query);
         out.writeStringArray(filteringAlias);
         if (fields != null) {
             out.writeBoolean(true);
diff --git a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
index f78b0ea2e6d..2910736031f 100644
--- a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
+++ b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
@@ -19,12 +19,10 @@
 
 package org.elasticsearch.action.explain;
 
-import org.elasticsearch.action.support.QuerySourceBuilder;
 import org.elasticsearch.action.support.single.shard.SingleShardOperationRequestBuilder;
 import org.elasticsearch.client.ElasticsearchClient;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Strings;
-import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.index.query.QueryBuilder;
 import org.elasticsearch.search.fetch.source.FetchSourceContext;
 
@@ -33,8 +31,6 @@ import org.elasticsearch.search.fetch.source.FetchSourceContext;
  */
 public class ExplainRequestBuilder extends SingleShardOperationRequestBuilder<ExplainRequest, ExplainResponse, ExplainRequestBuilder> {
 
-    private QuerySourceBuilder sourceBuilder;
-
     ExplainRequestBuilder(ElasticsearchClient client, ExplainAction action) {
         super(client, action, new ExplainRequest());
     }
@@ -87,15 +83,7 @@ public class ExplainRequestBuilder extends SingleShardOperationRequestBuilder<Ex
      * Sets the query to get a score explanation for.
      */
     public ExplainRequestBuilder setQuery(QueryBuilder query) {
-        sourceBuilder().setQuery(query);
-        return this;
-    }
-
-    /**
-     * Sets the query to get a score explanation for.
-     */
-    public ExplainRequestBuilder setQuery(BytesReference query) {
-        sourceBuilder().setQuery(query);
+        request.query(query);
         return this;
     }
 
@@ -151,28 +139,4 @@ public class ExplainRequestBuilder extends SingleShardOperationRequestBuilder<Ex
         }
         return this;
     }
-
-    /**
-     * Sets the full source of the explain request (for example, wrapping an actual query).
-     */
-    public ExplainRequestBuilder setSource(BytesReference source) {
-        request().source(source);
-        return this;
-    }
-
-    @Override
-    protected ExplainRequest beforeExecute(ExplainRequest request) {
-        if (sourceBuilder != null) {
-            request.source(sourceBuilder);
-        }
-        return request;
-    }
-
-    private QuerySourceBuilder sourceBuilder() {
-        if (sourceBuilder == null) {
-            sourceBuilder = new QuerySourceBuilder();
-        }
-        return sourceBuilder;
-    }
-
 }
diff --git a/core/src/main/java/org/elasticsearch/action/explain/TransportExplainAction.java b/core/src/main/java/org/elasticsearch/action/explain/TransportExplainAction.java
index e52d4e32071..fbed8531c20 100644
--- a/core/src/main/java/org/elasticsearch/action/explain/TransportExplainAction.java
+++ b/core/src/main/java/org/elasticsearch/action/explain/TransportExplainAction.java
@@ -121,7 +121,7 @@ public class TransportExplainAction extends TransportSingleShardAction<ExplainRe
         SearchContext.setCurrent(context);
 
         try {
-            context.parsedQuery(indexService.queryParserService().parseTopLevelQuery(request.source()));
+            context.parsedQuery(indexService.queryParserService().toQuery(request.query()));
             context.preProcess();
             int topLevelDocId = result.docIdAndVersion().docId + result.docIdAndVersion().context.docBase;
             Explanation explanation = context.searcher().explain(context.query(), topLevelDocId);
diff --git a/core/src/main/java/org/elasticsearch/rest/action/explain/RestExplainAction.java b/core/src/main/java/org/elasticsearch/rest/action/explain/RestExplainAction.java
index 7c01fddf3cc..086446fc53f 100644
--- a/core/src/main/java/org/elasticsearch/rest/action/explain/RestExplainAction.java
+++ b/core/src/main/java/org/elasticsearch/rest/action/explain/RestExplainAction.java
@@ -22,17 +22,16 @@ package org.elasticsearch.rest.action.explain;
 import org.apache.lucene.search.Explanation;
 import org.elasticsearch.action.explain.ExplainRequest;
 import org.elasticsearch.action.explain.ExplainResponse;
-import org.elasticsearch.action.support.QuerySourceBuilder;
 import org.elasticsearch.client.Client;
 import org.elasticsearch.common.Strings;
+import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentBuilderString;
 import org.elasticsearch.index.get.GetResult;
-import org.elasticsearch.index.query.Operator;
-import org.elasticsearch.index.query.QueryBuilders;
-import org.elasticsearch.index.query.QueryStringQueryBuilder;
+import org.elasticsearch.index.query.QueryBuilder;
+import org.elasticsearch.indices.query.IndicesQueriesRegistry;
 import org.elasticsearch.rest.*;
 import org.elasticsearch.rest.action.support.RestActions;
 import org.elasticsearch.rest.action.support.RestBuilderListener;
@@ -50,9 +49,12 @@ import static org.elasticsearch.rest.RestStatus.OK;
  */
 public class RestExplainAction extends BaseRestHandler {
 
+    private final IndicesQueriesRegistry indicesQueriesRegistry;
+
     @Inject
-    public RestExplainAction(Settings settings, RestController controller, Client client) {
+    public RestExplainAction(Settings settings, RestController controller, Client client, IndicesQueriesRegistry indicesQueriesRegistry) {
         super(settings, controller, client);
+        this.indicesQueriesRegistry = indicesQueriesRegistry;
         controller.registerHandler(GET, "/{index}/{type}/{id}/_explain", this);
         controller.registerHandler(POST, "/{index}/{type}/{id}/_explain", this);
     }
@@ -65,22 +67,11 @@ public class RestExplainAction extends BaseRestHandler {
         explainRequest.preference(request.param("preference"));
         String queryString = request.param("q");
         if (RestActions.hasBodyContent(request)) {
-            explainRequest.source(RestActions.getRestContent(request));
+            BytesReference restContent = RestActions.getRestContent(request);
+            explainRequest.query(RestActions.getQueryContent(restContent, indicesQueriesRegistry, parseFieldMatcher));
         } else if (queryString != null) {
-            QueryStringQueryBuilder queryStringBuilder = QueryBuilders.queryStringQuery(queryString);
-            queryStringBuilder.defaultField(request.param("df"));
-            queryStringBuilder.analyzer(request.param("analyzer"));
-            queryStringBuilder.analyzeWildcard(request.paramAsBoolean("analyze_wildcard", false));
-            queryStringBuilder.lowercaseExpandedTerms(request.paramAsBoolean("lowercase_expanded_terms", true));
-            queryStringBuilder.lenient(request.paramAsBoolean("lenient", null));
-            String defaultOperator = request.param("default_operator");
-            if (defaultOperator != null) {
-                queryStringBuilder.defaultOperator(Operator.fromString(defaultOperator));
-            }
-
-            QuerySourceBuilder querySourceBuilder = new QuerySourceBuilder();
-            querySourceBuilder.setQuery(queryStringBuilder);
-            explainRequest.source(querySourceBuilder);
+            QueryBuilder<?> query = RestActions.urlParamsToQueryBuilder(request);
+            explainRequest.query(query);
         }
 
         String sField = request.param("fields");
diff --git a/plugins/lang-groovy/src/test/java/org/elasticsearch/messy/tests/IndicesRequestTests.java b/plugins/lang-groovy/src/test/java/org/elasticsearch/messy/tests/IndicesRequestTests.java
index 15c77960ead..4291f00bf1a 100644
--- a/plugins/lang-groovy/src/test/java/org/elasticsearch/messy/tests/IndicesRequestTests.java
+++ b/plugins/lang-groovy/src/test/java/org/elasticsearch/messy/tests/IndicesRequestTests.java
@@ -76,7 +76,6 @@ import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.action.search.SearchType;
 import org.elasticsearch.action.suggest.SuggestAction;
 import org.elasticsearch.action.suggest.SuggestRequest;
-import org.elasticsearch.action.support.QuerySourceBuilder;
 import org.elasticsearch.action.termvectors.MultiTermVectorsAction;
 import org.elasticsearch.action.termvectors.MultiTermVectorsRequest;
 import org.elasticsearch.action.termvectors.TermVectorsAction;
@@ -96,33 +95,16 @@ import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.ESIntegTestCase.ClusterScope;
 import org.elasticsearch.test.ESIntegTestCase.Scope;
 import org.elasticsearch.threadpool.ThreadPool;
-import org.elasticsearch.transport.Transport;
-import org.elasticsearch.transport.TransportChannel;
-import org.elasticsearch.transport.TransportModule;
-import org.elasticsearch.transport.TransportRequest;
-import org.elasticsearch.transport.TransportRequestHandler;
-import org.elasticsearch.transport.TransportService;
+import org.elasticsearch.transport.*;
 import org.junit.After;
 import org.junit.Before;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.List;
-import java.util.Map;
-import java.util.Set;
+import java.util.*;
 import java.util.function.Supplier;
 
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertNoFailures;
-import static org.hamcrest.Matchers.emptyIterable;
-import static org.hamcrest.Matchers.equalTo;
-import static org.hamcrest.Matchers.greaterThan;
-import static org.hamcrest.Matchers.hasItem;
-import static org.hamcrest.Matchers.instanceOf;
+import static org.hamcrest.Matchers.*;
 
 @ClusterScope(scope = Scope.SUITE, numClientNodes = 1, minNumDataNodes = 2)
 public class IndicesRequestTests extends ESIntegTestCase {
@@ -307,7 +289,7 @@ public class IndicesRequestTests extends ESIntegTestCase {
         String explainShardAction = ExplainAction.NAME + "[s]";
         interceptTransportActions(explainShardAction);
 
-        ExplainRequest explainRequest = new ExplainRequest(randomIndexOrAlias(), "type", "id").source(new QuerySourceBuilder().setQuery(QueryBuilders.matchAllQuery()));
+        ExplainRequest explainRequest = new ExplainRequest(randomIndexOrAlias(), "type", "id").query(QueryBuilders.matchAllQuery());
         internalCluster().clientNodeClient().explain(explainRequest).actionGet();
 
         clearInterceptedActions();
@@ -684,24 +666,6 @@ public class IndicesRequestTests extends ESIntegTestCase {
             }
         }
     }
-
-    private static void assertSameIndicesOptionalRequests(String[] indices, String... actions) {
-        assertSameIndices(indices, true, actions);
-    }
-
-    private static void assertSameIndices(String[] indices, boolean optional, String... actions) {
-        for (String action : actions) {
-            List<TransportRequest> requests = consumeTransportRequests(action);
-            if (!optional) {
-                assertThat("no internal requests intercepted for action [" + action + "]", requests.size(), greaterThan(0));
-            }
-            for (TransportRequest internalRequest : requests) {
-                assertThat(internalRequest, instanceOf(IndicesRequest.class));
-                assertThat(internalRequest.getClass().getName(), ((IndicesRequest)internalRequest).indices(), equalTo(indices));
-            }
-        }
-    }
-
     private static void assertIndicesSubset(List<String> indices, String... actions) {
         //indices returned by each bulk shard request need to be a subset of the original indices
         for (String action : actions) {
@@ -820,26 +784,26 @@ public class IndicesRequestTests extends ESIntegTestCase {
 
         @Override
         public <Request extends TransportRequest> void registerRequestHandler(String action, Supplier<Request> request, String executor, boolean forceExecution, TransportRequestHandler<Request> handler) {
-            super.registerRequestHandler(action, request, executor, forceExecution, new InterceptingRequestHandler(action, handler));
+            super.registerRequestHandler(action, request, executor, forceExecution, new InterceptingRequestHandler<>(action, handler));
         }
 
         @Override
         public <Request extends TransportRequest> void registerRequestHandler(String action, Supplier<Request> requestFactory, String executor, TransportRequestHandler<Request> handler) {
-            super.registerRequestHandler(action, requestFactory, executor, new InterceptingRequestHandler(action, handler));
+            super.registerRequestHandler(action, requestFactory, executor, new InterceptingRequestHandler<>(action, handler));
         }
 
-        private class InterceptingRequestHandler implements TransportRequestHandler {
+        private class InterceptingRequestHandler<T extends TransportRequest> implements TransportRequestHandler<T> {
 
-            private final TransportRequestHandler requestHandler;
+            private final TransportRequestHandler<T> requestHandler;
             private final String action;
 
-            InterceptingRequestHandler(String action, TransportRequestHandler requestHandler) {
+            InterceptingRequestHandler(String action, TransportRequestHandler<T> requestHandler) {
                 this.requestHandler = requestHandler;
                 this.action = action;
             }
 
             @Override
-            public void messageReceived(TransportRequest request, TransportChannel channel) throws Exception {
+            public void messageReceived(T request, TransportChannel channel) throws Exception {
                 synchronized (InterceptingTransportService.this) {
                     if (actions.contains(action)) {
                         List<TransportRequest> requestList = requests.get(action);