Numerical schemes for ductile fracture simulations have advanced with improved porous plasticity models, such as the shear-modified Gurson-Tvergaard-Needleman (GTN) model. However, conventional implementations struggle to predict fracture accurately under low stress triaxiality conditions. A prior study extended the shear-modified GTN model with a non-local integral approach to prevent pathological mesh dependency and spurious strain localization by incorporating two distinct length scales accounting for failure modes observed at higher and lower triaxial stress states. Although the model accurately predicts complex fracture behaviors such as shear progression of failure from flat dimple rupture with sufficient separation of length scales, its implementation in Abaqus/Explicit (VUMAT) is computationally expensive due to the need for smaller time steps. In this work, an implicit formulation is employed where the constitutive material response is updated in a staggered manner, with each iteration solving the mechanical states and porosity evolution separately using the Newton-Raphson iteration method. The mechanical state is first updated by assuming constant porosity, followed by porosity evolution, improving computational efficiency and stability and making it suitable for complex structural simulations. Furthermore, we incorporate a micromechanics-based void coalescence criterion to deter mine the critical porosity at which coalescence initiates and accelerates damage evolution. This approach replaces the conventional threshold-based acceleration of damage evolution in the GTN model with a more physically accurate description of void coalescence and crack initiation. This improvement significantly improves failure predictions under shear-dominated conditions, where traditional GTN models tend to underestimate damage evolution. Comparisons with the experimental data and VUMAT results highlight the improved accuracy and computational efficiency of the implicit model. The proposed methodology offers a more computationally efficient, physically motivated framework for modeling ductile fracture in structural components subjected to complex loading scenarios.