Simple 7s Performance Analysis

chess_boardAnalyzing sevens is not easy. Sevens lacks the familiar structure imposed by fifteens set piece and phase play. Matches are fast paced and chaotic. Listening to a team break down a sevens match often sounds like the disjointed recollections of crime scene witnesses.

This post introduces a notational system for tracking sevens performance that uses ball possession as the fundamental unit of analysis.  A possession is a scoring opportunity. It begins when a team takes ownership of the ball and ends with either a score, a turn over, or a referee’s stoppage due to time expiring. Possessions alternate between teams through the course of the match providing a convenient structure for notating sevens play.

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Time of Possession: technical aspects

This blog post summarizes the technical details of how the data and graphics in Analyzing time of Possession in 7s were generated. Writing that blog post was an educational exercise to get familiar with the Python statistical programming ecosystem. Up until this point, most of the analysis work at Starting 7s was conducted in the R programming language. Inspired by the words of educational technologist Seymour Papert*, who famously said “You can’t think seriously about thinking without thinking about thinking about something,” this analysis and blog post were conducted in a similar spirit. You can’t seriously learn to use a new tool without learning to use the new tool to do something.

The remainder of this blog post describes the tools and techniques used to conduct the possession analysis in Python.

* Perhaps not coincidentally, it is worth noting that Seymour Papert was South African, and occasionally used rugby examples to animate his thought experiments.

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Analyzing time of Possession in 7s

 

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World Rugby tracks time of possession for all World Rugby Sevens Series matches. Starting 7s recently published an analysis of time of possession data from the 2014-2015 series in order to understand its impact on 7s gameplay. The analysis considered:

  • The relationship between possession and scoring
  • The relationship between possession and winning
  • The impact of possession in matches including non-core teams

This blog post discusses the article’s findings and shares some directions for future analysis.

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7 Habits for Highly Effective 7s — Part one: Leg drive

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The 7 Habits of Highly Effective People, first published in 1989, is a popular self help book. It presents an approach to attaining goals by following a few universal principles centered around character and ethics. This post is the first in a series to introduce 7 habits for highly effective 7s. Like Covey’s habits, these habits are universally practiced by effective 7s players regardless of body type, position, team tactics, or strategy.

The first habit is leg drive. Effective 7s players drive their legs in contact with short, sharp steps. As the following video clips demonstrate, strong leg drive generates turnovers on defense and scoring opportunities on attack.

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Visualizing directional tackle data

Tackle

Sports coaches are not always interested in the statistics, graphs, and charts that their analysts produce. However, in my experience, rugby and American football coaches are always interested in tackle data.  One on one tackling is the cornerstone of team defense in both sports. Missed tackles lead to big plays. They are usually the difference between a good and bad defense. So it is easy to understand why coaches are so interested in tackle data. But assessing tackle performance is notoriously difficult.

Starting 7s recently published an article on Rpubs describing an approach to visualizing tackle data. It categorizes tackle attempts by the clock face number that corresponds to the tackler’s tracking angle relative to the ball carrier. We plot the data using polar coordinate charts that map tackles to their corresponding clock face numbers. Using this approach coaches can quickly see where the majority of their team’s — or their opponent’s — tackle attempts are made and missed.

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A tale of two (NFL) tackles — JJ Watt and Luke Kuechly

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wsj.com recently published an article called What the NFL Can Learn From Rugby. It describes the growing trend of American football coaches learning safer and more effective tackling techniques from rugby.

The article does a great job of pointing out the differences between cheek to cheek rugby tackles and across the bow football tackles. However, two tackles made during the 2015 NFL season’s opening weekend do a better job of showing the differences:

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