Gennaro Gattuso is still searching for his first victory after an inexperienced Milan side slumped to defeat in Croatia on Thursday.
New boss Gattuso decided to field a side with an average age of 21 as the Rossoneri were already assured of qualification for the knockout phase of the Europa League as Group D winners.
But his hopes of a morale-boosting victory in his second game in charge were dashed by a goal in each half by Jakov Puljic and Mario Gavranovic.
More to follow
New boss Gennaro Gattuso has drawn and lost his two games in charge at Milan
Forward Jakov Puljic put Rijeka ahead with a free kick in the seventh minute on Thursday