diff --git a/litellm/main.py b/litellm/main.py
index 271c54e514d..69c9121893f 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -348,6 +348,13 @@ def mock_completion(
             prompt_tokens=10, completion_tokens=20, total_tokens=30
         )
 
+        try:
+            _, custom_llm_provider, _, _ = litellm.utils.get_llm_provider(model=model)
+            model_response._hidden_params["custom_llm_provider"] = custom_llm_provider
+        except:
+            # dont let setting a hidden param block a mock_respose
+            pass
+
         return model_response
 
     except:
diff --git a/litellm/router.py b/litellm/router.py
index b15687f677e..38ebcc1c940 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -997,6 +997,9 @@ class Router:
                         """
                         try:
                             kwargs["model"] = mg
+                            kwargs.setdefault("metadata", {}).update(
+                                {"model_group": mg}
+                            )  # update model_group used, if fallbacks are done
                             response = await self.async_function_with_retries(
                                 *args, **kwargs
                             )
@@ -1025,8 +1028,10 @@ class Router:
                                 f"Falling back to model_group = {mg}"
                             )
                             kwargs["model"] = mg
-                            kwargs["metadata"]["model_group"] = mg
-                            response = await self.async_function_with_retries(
+                            kwargs.setdefault("metadata", {}).update(
+                                {"model_group": mg}
+                            )  # update model_group used, if fallbacks are done
+                            response = await self.async_function_with_fallbacks(
                                 *args, **kwargs
                             )
                             return response
@@ -1191,6 +1196,9 @@ class Router:
                             ## LOGGING
                             kwargs = self.log_retry(kwargs=kwargs, e=original_exception)
                             kwargs["model"] = mg
+                            kwargs.setdefault("metadata", {}).update(
+                                {"model_group": mg}
+                            )  # update model_group used, if fallbacks are done
                             response = self.function_with_fallbacks(*args, **kwargs)
                             return response
                         except Exception as e:
@@ -1214,6 +1222,9 @@ class Router:
                             ## LOGGING
                             kwargs = self.log_retry(kwargs=kwargs, e=original_exception)
                             kwargs["model"] = mg
+                            kwargs.setdefault("metadata", {}).update(
+                                {"model_group": mg}
+                            )  # update model_group used, if fallbacks are done
                             response = self.function_with_fallbacks(*args, **kwargs)
                             return response
                         except Exception as e:
diff --git a/litellm/tests/test_router_fallbacks.py b/litellm/tests/test_router_fallbacks.py
index 29bc0d7bf1e..5d17d36c9f7 100644
--- a/litellm/tests/test_router_fallbacks.py
+++ b/litellm/tests/test_router_fallbacks.py
@@ -716,7 +716,7 @@ def test_usage_based_routing_fallbacks():
         # Constants for TPM and RPM allocation
         AZURE_FAST_TPM = 3
         AZURE_BASIC_TPM = 4
-        OPENAI_TPM = 2000
+        OPENAI_TPM = 400
         ANTHROPIC_TPM = 100000
 
         def get_azure_params(deployment_name: str):
@@ -775,6 +775,7 @@ def test_usage_based_routing_fallbacks():
             model_list=model_list,
             fallbacks=fallbacks_list,
             set_verbose=True,
+            debug_level="DEBUG",
             routing_strategy="usage-based-routing",
             redis_host=os.environ["REDIS_HOST"],
             redis_port=os.environ["REDIS_PORT"],
@@ -783,17 +784,32 @@ def test_usage_based_routing_fallbacks():
         messages = [
             {"content": "Tell me a joke.", "role": "user"},
         ]
-
         response = router.completion(
-            model="azure/gpt-4-fast", messages=messages, timeout=5
+            model="azure/gpt-4-fast",
+            messages=messages,
+            timeout=5,
+            mock_response="very nice to meet you",
         )
         print("response: ", response)
         print("response._hidden_params: ", response._hidden_params)
-
         # in this test, we expect azure/gpt-4 fast to fail, then azure-gpt-4 basic to fail and then openai-gpt-4 to pass
         # the token count of this message is > AZURE_FAST_TPM, > AZURE_BASIC_TPM
         assert response._hidden_params["custom_llm_provider"] == "openai"
 
+        # now make 100 mock requests to OpenAI - expect it to fallback to anthropic-claude-instant-1.2
+        for i in range(20):
+            response = router.completion(
+                model="azure/gpt-4-fast",
+                messages=messages,
+                timeout=5,
+                mock_response="very nice to meet you",
+            )
+            print("response: ", response)
+            print("response._hidden_params: ", response._hidden_params)
+            if i == 19:
+                # by the 19th call we should have hit TPM LIMIT for OpenAI, it should fallback to anthropic-claude-instant-1.2
+                assert response._hidden_params["custom_llm_provider"] == "anthropic"
+
     except Exception as e:
         pytest.fail(f"An exception occurred {e}")