A tool for improving identification of one or more storage system elements responsible for a performance degradation in a digital storage system. The tool records performance metric data for the one or more storage system elements in a database. The tool locates one or more outliers in the performance metric data for a focus time window using a statistical criterion. The tool calculates a problem contribution probability value for at least one of the one or more outliers. The tool determines a sequential list of outliers, wherein an order in the sequential list of outliers is determined using the problem contribution probability value.