Complex systems analysis in rugby union

Abstract

The use of performance capturing methods to evaluate player and team behaviours is common practice in rugby union performance analysis. An emerging area of interest in other team sports is assessing performance through a complex systems lens. This view broadly describes performance as the resultant emergent behaviour from the interactions between players and the environment. The aims of the thesis were to advance knowledge on successful rugby union performance by determining the current state of rugby union performance analysis, understanding the perspectives and needs of elite coaches, assessing the utility of novel spatial-temporal metrics to capture collective behaviours, and assessing the influence of collective behaviours and contextual factors on try scoring.
Chapter One provides an overview of the topic of performance analysis and a rationale for subsequent experimental studies. Chapter Two (Study One) details a critical systematic review of the performance analysis in rugby literature and highlights advancements made in other team sports. Chapter Three provides a 2025 update to the published systematic review, offering a contemporary overview of current performance analysis research. Forty-eight studies were reviewed across both studies, revealing persistent methodological limitations in the assessment of rugby union performance. Performance indicators remain the dominant evaluative approach; however, a small number of studies modelled team behaviours through a complex systems lens. Team sports such as association football have progressed analytical measures to capture the emergent and interactive dynamics of performance. Rugby has been slow to adopt integrative system-based methodologies, remaining underdeveloped relative to association football in the advancement of performance analysis approaches.
Chapter Four (Study Two) reports a qualitative analysis which explored the tactical determinants of successful performance from the perspective of three international-level expert rugby coaches. This research extended the findings of the critical reviews by examining key tactical principles and their practical application. Common themes among the coaches included the importance of tactical kicking, defensive adaptability and set-piece proficiency. The qualitative approach revealed consistent themes across international-level coaches, including the importance of gaining territory through an effective kicking strategy, rapid reorganisation ii following turnovers, and context-dependent decision-making. However, a disconnect remains between empirical research and coaching practice, largely due to limited contextualisation in performance metrics, and under-utilisation of coaches’ experiential knowledge in research design.
Chapter Five (Study Three) explored the utility and application of novel spatial-temporal metrics to assess critical events in professional rugby. The distance between centroids, stretch index and convex hull were applied to both teams’ positional data to capture emergent (movement) behaviours during successful attacking phases. These metrics were selected due to their application in other team sports to provide global insights into team tactics, positioning and strategies that make up their collective tactical behaviours. The analysis focused on ten try-scoring events from two-teams competing in a single professional match. Successful attacking phases were characterised by higher stretch index values (attack vs defence; 14.3±1.1 m vs 13.0±0.8 m in the Defensive 22-40 zone and 14.1±0.8 m vs 12.7±0.2 m; mean ± SD in the Defensive 40-50m zone), indicating deliberate attacking spatial expansion to stretch defensive structures and create scoring opportunities. In response to these collective behaviours, defending teams exhibited higher stretch index approximate entropy (ApEn) (attack vs defence; 0.19±0.02 vs 0.27±0.02 and 0.24±0.03 vs 0.30±0.02; mean ± SD, scale range 0-2), evidence of greater movement irregularity and defensive instability. These outcomes provide evidence that attacking effectiveness is related to spatial expansion, while defensive stability appears to rely on structured coordination.
Chapter Six (Study Four) extended the application of collective tactical variables to a larger dataset, examining team behaviours in relation to their immediate contextual environment. An observational analysis was conducted on 43 try-scoring events, using positional data from 118 professional rugby players across six matches. Each 30-second period preceding a try was analysed incorporating contextual factors such as the preceding event, field location and match quarter to determine behaviours related to certain constraints. Tries from linebreaks (10.2 ± 3.2 m between teams; mean ± SD) and mauls (13.1 ± 6.1 m) occurred at greater centroid distances, whereas those following tackle breaks (6.7 ± 1.8 m) were associated with reduced inter-team spacing. Centroid distance ApEn was highest in offloads (0.23±0.11) and wide passes (0.23±0.15), reflecting increased unpredictability, particularly in the first quarter. It appears that the combination of collective team behaviour, preceding attacking events, and field location influence try-scoring in rugby union.
Collectively, the outcomes of the systematic review, coach interviews, and spatio-temporal match analyses highlighted the current state of performance analysis in rugby union. The interviews revealed recurring themes among international coaches, highlighting the importance of contextualising performance and developing ecologically relevant performance measures that align with the practical demands of training and international competition The observational studies were the first to investigate spatial-temporal metrics to assess how collective team behaviours shape try-scoring in male professional rugby union. Given the limited research investigating collective tactical behaviours in professional rugby union, the research outcomes offer valuable insights to support the integration of spatial-temporal analysis into elite rugby union training and competitions.

Date of Award	2025
Original language	English
Supervisor	Andrew MCKUNE (Supervisor), David PYNE (Supervisor) & Ben SERPELL (Supervisor)