— The Chase (@thechasesport) September 25, 2017
Author: The Chase
The Lions’ Saturday team has produced two dominant defensive performances against the Crusaders and the New Zealand Maori, but will face their greatest challenge in Eden Park on Saturday. What can we learn about this contest from the Crusaders’ lack of success with ball in hand in Christchurch, and the All Blacks’ attacking dominance against Samoa?
Using statistical evidence to judge defensive performance
Nick Bishop’s recent article on the apparent growing divergence between analysis and statistics was surprising and disappointing. The Leinster analyst – who also worked with Stuart Lancaster for England – uses a single metric to support this, and the article seems to suggest only that there is a growing divergence between analysis and the use of tackle percentage as a viable metric of defensive performance. Indeed, some of Bishop’s own work is testament to how using statistics alongside technical and visual analysis can be persuasive and effective.
Bishop’s piece is a classic example of sporting scepticism of statistical study, and is of a piece with articles by mainstream journalists citing a number to support their case and feeling the need to include the standard disclaimer ‘statistics don’t tell the whole story’. A particular instance of poor statistical analysis does not invalidate the entire field, in the same way that a particular instance of poor tactical analysis does not invalidate that field. If anything, Bishop’s piece serves as an excellent piece of statistical analysis itself, disputing any presumption of correlation between defensive performance and tackle completion percentage by using evidence to support his argument. The next step is to work out what are effective metrics for describing different types of defence, and the 2016 Hurricanes are a good case study.
Tactical analysis: what rugby can learn from football
Technical and tactical analysis has come to flourish in rugby over the past few seasons, but is still far behind many leading team sports in terms of its detail and clarity. This is partly due to the tactical complexity of rugby relative to sports such as basketball and football: its multiple methods of scoring points bring with them numerous possible strategies to attempt to ‘optimise’ performance, and this adds layers of noise for an analyst trying to establish the signal.
Football’s single mode of scoring allows an analyst to establish a clear framework through which each player’s actions and decisions can be judged: an action’s worth can be determined by the extent to which it has increased its own team’s chances of creating a shot on goal in a high quality location, or decreased the opposition’s chances of doing so. The basis of football strategy is essentially shot creation and shot prevention, but rugby strategy cannot be condensed in the same fashion; rugby’s multiple modes of scoring – and multiple methods of achieving the same scoring action – bring with them more strategic options. One coach may decide that the most efficient way of optimising his team’s performance is by gaining territorial advantage through their open-play kicking game, while another will opt to try and break through the opposition’s defensive line with passing skills and good spacing; a player’s actions and decisions must be judged with reference to this tactical framework to a greater degree than in other sports.
As a result of football’s relative simplicity in this regard, statistical and tactical analysis of the sport has flourished. A player’s passes can be judged based on the quality of shot that they result in, and a team’s attacking shape can be appraised based on the efficiency with which it allows progression of the ball into areas of the pitch where high-quality shots can be taken.
Statistical analysis in rugby is struggling to get past the stage of ‘Player X played well because he carried the ball Y times & made Z tackles’, but potential is there at a team-tactical level: Murray Kinsella’s detailed try analyses show this, as they attempt to take the key elements of a team’s attack and use data to assess them. At a tactical level, there are very few occasions on which we state definitively ‘Team A’s gameplan was to do X and Y in order to cause outcome Z’, using visual evidence to support the thesis, in the manner that sites such as Spielverlagerung can with football.