Methods and structures within a SAS expander for detecting link level errors in PHYs of a SAS expander to reduce overhead bandwidth utilization of SAS links between SAS initiators and SAS expanders. In one aspect hereof, a SAS expander self monitors the error status registers of its own PHYs over an internal path that does not use bandwidth of the attached SAS links. When a link level error is so detected the SAS expander may initiate actions and/or report the error to a SAS initiator to thereby reduce the potential for lost data integrity. Where multiple SAS expanders are configured in a SAS domain fabric, each expander may monitor its PHYs or one expander may be designated a master and monitor PHYs of all expanders in the fabric.