Ribs are essential functional elements in injection-molded polymer components, providing stiffness and strength in lightweight, thin-walled designs. In hybrid structures, such as ribs on organo-sheet substrates, the mechanical performance of the rib–substrate interface is critical. At the rib root, stress concentrations and residual stresses may reduce joint strength. Targeted redirection of reinforcing fibers from the organo-sheet into the rib base during injection molding is a promising strategy to migration and reorientation. This work focuses on developing and evaluating semi-analytical and simulation-based approaches to predict stress states in the rib region. Sparse in-mold measurements, consisting of two combined pressure–temperature sensors and process data from the injection nozzle (pressure and volumetric flow), are incorporated into the models to assess their potential for inferring local shear stresses. Computational fluid dynamics simulations using commercial injection molding software (Autodesk Moldflow) provide detailed fields of pressure, velocity, and shear stress, which are compared to simplified analytical estimates. Special emphasis is placed on the influence of key process parameters, such as injection speed, melt temperature, and material type, on the predicted stress distributions. Where possible, obtained results are validated by experimental trials. The results indicate that even minimal sensor input, when integrated with analytical and simulation models, may offer insights into local stress conditions relevant for fiber orientation and rib bonding. Future work will further evaluate the reliability and accuracy of these predictions under varying process conditions. This approach has the potential to support process understanding and optimization for fiber-reinforced injection-molded ribs.