Some more lockdown fun with some statistical modelling on try scorers.
As mentioned in a previous post, I’ve been working on a try scoring model to try and identify who really are the best try scorers.
After quite a bit of work involving 1,711 games, 3,292 players and over 350,000 data points from the 2013-20 seasons, I have developed a good model that predicts the number of tries scored based on:
The model has a goodness of fit rating (Multiple R) of 97.17% with a standard error of +/- 0.94 tries, so it’s very accurate in predicting how many tries a player should score based on the above factors.
The logic to rate try scorers is to use the model’s formula to work out how many tries a player should have scored based on their above performance factors. Then, subtract the number of tries they actually have scored to get a Tries Above/Below Expectation figure. From that, you can then calculate a % of tries they have scored above or below expectation.
For example, if the model suggested that Player X should have scored 10 tries this season based on their Position, Team Tries, Runs, Metres gained, Line Breaks and Tackle breaks, but they have only scored 8 tries, then their Tries Above/Below Expectation would be -2. Expressed as a % of their expected tries this would produce a rating of -25% (-2 divided by 8, multiplied by 100).
This % rating allows you to compare players who have scored different numbers of tries.
The position factor was calculated from the distribution of tries across all positions from the 2013-20 seasons. This effectively compensates players who play in positions that historically don’t score a lot of tries. So if a player scores more tries than average for that position, their rating will be higher. The model works similarly for the other performance factors as well.
So without further adieu, onto the ratings below.
I used a cut-off of 6 tries because that is what the NRL uses for their current leading try scorers, plus with a small number of tries the model can produce some volatile (eg fluke) results.
NRL Leading Try Scorers 2021: up to Round 18
|Rank||Name||Tries||Expected tries||Tries Above/Below Expectation||% Tries Above/Below Expectation|
I know some people will look at this list and see some good try scorers like our own Alex Johnston and Maka Sivo down the list in negative territory, and say this is garbage, but what this model shows is that for the amount of runs, metres, tackle breaks and line breaks they have made, plus the opportunities given to them by virtue of their position, they should have really scored more tries and so are rated as underperforming.
Bombed tries will negatively impact a player’s rating because they usually make a combination of metres, tackle breaks and line breaks before they don’t score the try.
Conversely, players with limited opportunities that “punch above their weight” and score tries will rate highly. Kevin Proctor, a prop who has scored 6 tries is the prime example here.