Alloplastic material is widely used for the reconstruction of calvarial defects. The objective of this article is to describe the effect of mechanical impact on a titanium calvarial implant and to discuss mechanical properties of alternative implant materials. The patient is a 19-year-old man who was involved in a traffic accident and underwent decompressive craniectomy for an extensive subdural hematoma. Reimplantation of the skull flap was complicated by infection and the flap had to be removed. The remaining cranial defect was closed with a titanium plate. The recovery was without complications. One year later, the patient was hit on the titanium plate, during a soccer match, by the elbow of a fellow player. The implant deflected inward, leaving a visible indentation of the cranial vault. Fortunately, there were no significant neurological symptoms and radiography did not show any signs of damage or pressure on the brain parenchyma. The patient had no aesthetic complaints regarding the shape. Thus, there was no indication to remove the plate. This case illustrates the limits of the protection offered by titanium cranioplasty.