Analysis on a full season of matches (n= 21) from a professional rugby union club in the Guinness Pro 14 and European competition from the 2017-18 season took place. BIP times were split into four categories of specific durations which were used to design the GRIT simulation. The same methodology occurred for ball-out-of-play (BOP) durations and categories. The subsequent BIP and BOP periods were combined in a stochastic nature to replicate specific match play demands. Power profile scores took place both prior (baseline) and post players completing the GRIT simulation to establish the performance decrement in terms of Whole Squad and Positional analysis. The tests used in the Power Profile scores were Countermovement Jump (CMJ), Banded-Bench Press and Speed Tests with variables to measure aspects of physiological performance appropriate for rugby union. Through Kruskal Wallis post-hoc analysis, each position (n= 8) was subject to their own demands as no positions could be grouped together. The BIP categories, Short (15s, n=17), Moderate (20s, n=12), Long (40s, n=7) and Very Long (90s, n=3) totalled 16 mins. The BOP categories, Short (15s, n= 17), Moderate (40s, n= 12), Long (54s, n=7) and Very Long (85s, n=3) totalled 22 mins 48s. The total duration of the GRIT simulation was 38mins 48s. GRIT simulation: The position Back 3 covered the greatest Total Distance (4001m) and Sprint Distance (310m) for the whole simulation. The position Hooker had the greatest number of collisions (n= 25) and the greatest Moderate Acceleration metres of the forwards unit (188m). Centres had the largest distance covered for High Speed Running metres (880m) with Back 3 having the largest distance covered in Hard Acceleration metres (68m). Power Profiling: Whole Squad analysis illustrated a small increase in Effect Sizes (ES) for the speed tests 0-10m, 0m-20m and 10m-20m (d = 0.25, d = 0.34 and d = 0.40, respectively). Trivial ES were seen for all variables of the CMJ (d < 0.20), and a mix of trivial and moderate ES were evident for Banded-Bench Press variables. The Backs unit group illustrated the largest increase compared to forwards (d = 1.08) for the 10-20m speed test. Forwards unit group illustrated larger decrements in Banded-Bench Press variables (concentric mean power (W), d = -1.02) and CMJ variables (mean velocity (m/s), d = -0.45) from pre to post GRIT simulation.