Analysis of Ruck Contact Exposure and Technical–Tactical Behaviors Related to Match Outcome in International Rugby Union

This study examined the association between technical–tactical ruck variables and the probability of defeat in international rugby union. Six variables (Pitch Territory, Number of Phases, Match Half, Player Type, Gainline Progression/Ruck Position, and Number of Players in the Ruck) were recorded from 2575 rucks across 26 international matches played by the Spanish national team. The binary logistic regression model displayed a significant overall fit (χ2 = 137.247, df = 9, p < 0.001, Nagelkerke R2 = 0.0692, AUC = 0.6208), achieving 57.98% global accuracy. A high Number of Phases (OR = 3.265 for ≥7 Phases), playing within Own Territory (OR = 1.481), operating Behind Gainline (OR = 1.478), or On Gainline (OR = 1.369), and actions during the Second Half (65.7%) compared to the First Half (54.5%) were significantly associated with higher odds of defeat. Conversely, the post hoc GLMM sensitivity check showed that the associations for these variables remained broadly consistent, while indicating that the exclusive involvement of Backs was associated with the highest estimated probability of defeat among the Player Type categories (64.4% vs. 57.2% for Forwards), and that the involvement of ≥4 players in the ruck became statistically significant in the mixed-effects model after accounting for match-level clustering and was associated with a higher estimated probability of defeat. In conclusion, Number of Phases, Pitch Territory, Gainline Progression, and the quantity and Player Type involved are significantly associated with defeat, aligning with specific contact exposure environments.