Other than the field goal, there are few more exciting kicking moments in rugby league than the correct execution of a 40/20. The 40/20, meaning that the kick is taken behind the player’s forty metre line, bounces in the field of play and goes into touch inside the opponent’s twenty metre, gives a huge advantage for the kicking team, as it advances the ball forty metres down the field and offers a fresh attacking set.
Introduced in 1997 for the Super League competition and retained for the NRL, the 40/20 doesn’t happen very often. You might see a successful attempt every five to ten games. Indeed, we see more field goals.
Just as a bit of a trivial aside, Daly Cherry-Evans has kicked the most 40/20s in the NRL between 2013 and 2018, with sixteen, or one every 8.8 games he has started. The other players in double digits are Chris Sandow (14), Cooper Cronk (12), Cameron Smith (11) and Blake Green (10). Funnily enough, probable Immortal Johnathan Thurston never kicked a 40/20 in this period.
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At one end of the scale, we have every NRL team. At the top level, we only see the short kick off when the clock is winding down and the team kicking off desperately needs points to remain in contention for the win. At the other end of the scale, we have the Ipswich Jets, coached by Shane and Ben Walker, who will indiscriminately use short kick-offs, short drop-outs and taking the two when it makes no sense to do so because that’s Walkerology. Are the Walker Brothers on to something that everyone else is missing?
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In 2018, I recorded a few outcomes for 1,000 sets of six. This sounds like a lot but it’s actually the equivalent of about twelve games of football. I looked at where the set started, what the end result of the set was (e.g. error, score, fifth tackle kick) and a few other details.
Poseidon ratings are a new team rating system for both the NRL and the Queensland Cup.
For those who don’t have time to read 2000+ words, here’s the short version: the purpose of Poseidon ratings is to assess the offensive and defensive capabilities of rugby league teams in terms of the number of tries they score and concede against the league average. By using these ratings, we can estimate how many tries will be scored/conceded in specific match ups and then use that, with probability distributions, to calculate an expected score, margin and winning probabilities for the match-up.
The biggest problem I face in trying to work through rugby league analytics is a lack of useful, reliable, easy to source data to analyse. For this post, I had to do it myself.
I recorded 1,000 sets of six from the 2018 season so far, ranging from a Titans-Warriors pre-season game and finishing during the Titans-Bulldogs game in round 15. A thousand may sound like a lot but given there are about 80 sets of six per game, it’s about a dozen games worth of material. We are working with a relatively small sample size and that the probabilities we estimate may not precisely align with reality. If I had the time and patience (a salary could substitute for time and patience), I could go through the entire history of the NRL and do a better job. This site’s motto is “you get what you pay for”.
But today is not about solving problems once and forever. There are a number of ways to solve a given problem and the techniques and data presented here are hopefully what will be a foundation to build upon. This post is about demonstrating that rugby league can be analysed statistically and useful conclusions can be drawn.