Work is slow waiting for others, so, following on from
@Wilson's effort above, I've noodled over to American sports and adapted something called the simple rating system (SRS). It's a rating system based on two components:
- The average points differential over the season
- The strength of schedule
It produces two metrics, the SRS and the strength of schedule (SoS). Both of these are measured in points relative to the statistical average for the competition. Or, relative to the hypothetical average team.
- SRS estimates how many points better/worse a team is that the average team, adjusted by the SoS
- SoS estimates how tough the schedule has been for each team, as measured by the SRS
For the SRS, if your team has a score of +7, then it means you're 7-points better than the average team. SRS at -3 means you're 3-points worse. The closer your SRS is to 0 the closer you are to being the average team. For the SoS, it measures how good their opponents have been. So if your team has an SoS of +5 then it means your opponents have typically been 5-points better than average.
The more big brained members of the class may have noticed that the two rely on each other. i.e., SRS is dependent on the SoS which is dependent on the opponents SRS, which is dependent on the SoS etc... It's an iterative process until the numbers basically level out. Further reading:
a blog explaining it using the NFL.
Results are below.
So, the SRS says that the Chiefs are currently +10.4 points better than the average team while the Drua are -10.5 points worse. By these ratings it would say that the Chiefs are 2.1 point favourites against the Crusaders (Chiefs SRS - Crusaders SRS = 10.4 - 8.3 = 2.1). To use the actual up-coming matches:
Crusaders are 6.16 point favourites against the Hurricanes
Chiefs are 18.41 point favourites against the Waratahs
Moana are 3.92 point favourites against the Blues
Highlanders are 7.61 point favourites against the Drua
Reds are 6.29 point favourites against the Brumbies
Overall I'd say the current strucutre looks about right with the top and bottom three and the big scrap from 4-8, where there is <5 SRS points between Moana and the Brumbies. In other words, games between everyone here are probably going to be particulatly close one score games.
Meanwhile, the SoS says the Blues have had the toughest schedule so far, having faced opponents that are typically 4.01 points better than average. This will be because 3/7 of their games have been against the Chiefs and Crusaders (the only team to do so atm, I believe). Meanwhile, the Brumbies have faced opponents that are typically 3.46 points worse than average, having only faced one above average team (Chiefs).
The SoS only considers performance and doesn't consider venue or travel, which can be important for Super Rugby. For e.g., a travel schedule of Perth -> Auckland -> Fiji -> Sydney would be viewed the same Wellington -> Hamilton -> Wellington -> Sydney.
Finally, and perhaps most importantly, the Blues SRS (-1.56) is better than the Brumbies SRS (-2.61). Suggesting that, when adjusted for their schedule strength, the Blues have performed slightly better overall this season and that the Breez are coasting by on easy games.
tldr: Blues > Bumbreez.