This paper focuses on the indeterminate protection challenge of the sensitivity deterioration (SD) (also known as protection blindness) of the overcurrent protection (OCP) devices due to the large-scale integration of distributed energy resources (DERs) in the unbalanced distribution networks (DNs). The protection blindness of the OCP has been demonstrated through novel mathematical formulation to quantify the percentage of the protection blindness for different type of distributed generation (DGs) units and for their varying penetration levels. In addition, this issue has been realistically analyzed for the different fault impedances to examine its impact on the traditional OCP system. A mitigation strategy has been proposed to overcome the SD issue of the OCP protective devices (PDs) for a robust detection and clearance of electrical faults by the OCP devices without the need for a costly upgradations of the protection system. This protection blindness issue has been explored and the mitigation strategies have been tested for both synchronous and inverter based DGs using the IEEE standardized test feeder. The results prove the effectiveness of the proposed mitigation strategy for their practical applications and suitability to improve the grid resilience.