It is widely accepted that fractures decrease the strength of rock masses in comparison to intact rock. This phenomenon is evaluated by rock mass classification systems, such as the Geological Strength Index (GSI). However, their predictive ability is limited when applied to larger scales and rocks with fracture anisotropy. In order to gain a fundamental understanding of the interplay between preexisting fractures, damage creation, and eventual failure, we model the rupture of fractured rock mass through numerical simulations. Additionally, our objective is to quantitatively assess the correlation between preexisting fracture networks and rock mass strength. To achieve this, we use the Synthetic Rock Mass (SRM) approach, which models the rock as an assembly of individual blocks embedded with in situ joint fabric using a Discrete Fracture Network (DFN) representation. Indicators are developed to quantify the induced damage in the stressed sample until failure.