Tag Archives: poisson

A glance at the NRL with Poseidon ratings

If you read my tips for round 1, you would have seen the Poseidon rating making an appearance. The purpose of the Poseidon rating system is to look at each team’s offensive and defensive capabilities separately, as well as their home and away performance, to see if their winning record is concealing strengths or weaknesses.

The underlying principle is quite simple. We look at how many tries a team scores, at home and away, and how many they conceded, similarly at home and away, and see how that stacks up against the league average over the previous twenty-four rounds.

The league average moves over time. In 2013, the home team scored 3.9 tries on average and the away team 3.2. In 2018, those numbers had changed to 3.6 and 3.1 respectively. While 0.3 tries per game may not seem like much, over a 192 game regular season schedule, that’s 57 tries that have gone missing, or about 316 points, just for the home teams.

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Primer – Poseidon ratings

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.

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