Weld Lines (WLs) appear frequently in the manufacturing of injection-molded thermoplastic parts and have a direct impact on their mechanical performance. In the literature, we can find an extensive list of papers, which describe the effect of WLs on the mechanical properties of reinforced thermoplastics, but the prediction of the mechanical properties in the vicinity of the WLs is still a challenging task. The formation of a WL during the injection molding of a short fiber-reinforced thermoplastic can induce locally particular morphologies/microstructures, which strongly affect the loading-dependent mechanical properties at the WL. In our vision, the most important local morphological/microstructural factors contributing to the mechanical performance at the WL are: Matrix healing, fiber orientation and molecular orientation. In such context, we propose a two-step simulation strategy for predicting the mechanical properties at the WL: 1) The modeling of the locally induced morphologies/microstructures at the WL, and 2) the correlation of the last ones with the mechanical properties of the composite material. This paper deals basically with the first step of the integrative simulation scheme. We present firstly the current situation of the prediction of the final position of a WL using standard injection molding software and we emphasize on the remaining challenges. In terms of the prediction of the quality of the matrix healing, we propose a physical model based on the reptation theory and we show its numerical implementation using commercial software. By comparing the fiber orientation measurements by computed tomography with the fiber orientation predictions at the WL using commercial software, we evidence that the macroscopic fiber orientation models still have room for improvement. Finally, we outlook the modelling of the process-induced molecular orientation and we describe the challenges of its implementation using commercial software for injection molding.