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Analysing the short-term impact of substitutes vs. starters in international rugby

The aim of this study was to compare the short-term performance of substitute players to starting players during International Rugby Union matches and determine how this performance was influenced by playing position, the timing of the substitution and the score margin between teams. Individual player performances (n = 298) for substitutes and the starters they replaced were observed across 17 matches played between tier 1 rugby nations. Performance was categorised as the total number of involvements, the number of attacking and defensive involvements, as well as the effectiveness of a player's performance for each of the above involvement categories. Results revealed forward substitutes performed more total (p = 0.001, ES = 0.61), attacking (p = 0.026, ES = 0.32) and defensive (p = 0.023, ES = 0.31) involvements than forward starters; however, there were no differences found for backs (p = 0.819–0.911). In addition, it was observed that an increase in score margin at the time of substitution led to a decrease in the total and attacking involvements per minute that a substitute performed, but an increase in defensive involvements for both forwards and backs. These findings provide a platform for coaches to make tactical decisions regarding substitution patterns during International Rugby matches. Specifically, coaches should prioritise forward substitutions over back substitutions, and implement tactical changes earlier in the second half to gain an advantage over the opposition.