2016 - Team Ratings After Round 5

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A number of victory margins were again this week quite divergent from what the three Team Rating Systems expected, whether those victories were measured in points, which is ChiPS' and MARS' key input, or in Scoring Shots, which is MoSSBODS' sole focus.

That, coupled with the fact that ChiPS and MoSSBODS are still in that part of the season where they're most responsive to surprises, has made for another week of substantial team re-rankings.

Even MARS though, which cares not whether a game is an early- or late-season game, shuffled 16 of the 18 teams, albeit only six by multiple places. It lifted Geelong two spots into 7th, GWS two spots into 8th, and Carlton two spots into 16th, and dropped West Coast out of top spot into 3rd, Adelaide from 4th to 6th, and the Gold Coast from 12th to 14th. It's hard to find serious fault with any of those changes, certainly not directionally.

ChiPS, for once, re-ranked fewer teams that MARS, leaving four unmoved, though three of its moves were more significant than any of MARS'. ChiPS lifted GWS up three places into 4th, dropped Port Adelaide three places into 13th, and also elevated Collingwood five places into 10th.

Its other multi-spot moves were to shunt the Dogs (now 7th), Saints (14th) and Dons (18th) down two places each, and to promote the Dees up two places into 11th.

Still the correlation between ChiPS and MARS Ratings remains high (+0.954) and only six team's rankings differ under the two Systems by more than one spot:

  • Western Bulldogs: 4th on MARS, 7th on ChiPS
  • GWS: 8th on MARS, 4th on ChiPS
  • Geelong: 5th on MARS, 8th on ChiPS
  • Port Adelaide: 9th on MARS, 13th on ChiPS
  • Collingwood: 12th on MARS, 10th on ChiPS
  • Melbourne: 13th on MARS, 11th on ChiPS

If ChiPS' ranking of GWS at 4 raises an eyebrow for you then MoSSBODS' ranking of them at 3 will probably raise the other (or leave the first with no more forehead to explore).

GWS' 31 Scoring Shots (SS) this week against a St Kilda side at home, with a hefty Net Venue benefit and with a Defence rated by MoSSBODS pre-game as only slightly below that of an average team, was enough to lift the Giants' Offensive ranking to 4th. Their concession of only 19 SS also lifted their Defensive rating, but only marginally, which saw their Defensive ranking slip to 6th. Overall, that meant an increase of about 1.6 SS in their Combined rating, which was enough to leapfrog them over the falling Eagles and Crows, and past the less-rapidly rising Hawks.

Looking more broadly at the MoSSBODS changes we see that it re-ranked 14 teams this week, 10 of them by multiple places.

The biggest rises were:

  • Collingwood, up 5 places into 11th
  • GWS, as noted, up 3 places into 3rd
  • Western Bulldogs, up 2 places into 2nd
  • Fremantle, up 2 places into 10th (a case of doing less badly than those just above you on the rankings)
  • Gold Coast, up 2 places into 12th

And the biggest falls were:

  • St Kilda, down 5 places into 14th
  • West Coast, down 3 places into 4th
  • Hawthorn, down 2 places into 5th
  • Brisbane Lions, down 2 places into 13th
  • Richmond, down 2 places into 15th

We can see how the teams currently arrange themselves in MoSSBODS' Ratings space by plotting their Ratings on a chart.  

A team's horizontal positioning on this chart reflects its Defensive Rating, its vertical positioning its Offensive Rating, and its distance from a grey, dotted line its Combined Rating, which is the sum of its Offensive and Defensive Rating.

Note that a team's proximity to a grey, dotted line should be measured at right angles to that line and not in terms of its horizontal or vertical distance from it. The Western Bulldogs, for example, are nearer to the Combined Rating = 6 line that are GWS, a fact that you can confirm by referring to the table of numerical Ratings above, which shows the Dogs with a Combined Rating of 5.63 and GWS with a Combined Rating of 5.29.

The addition of the grey, dotted lines allows you to see, for example, that Adelaide's Combined Rating is greater than Geelong's, a fact that would otherwise be hard to ascertain given the distance between these two teams in the Offensive-Defensive Rating space. 

Based on this chart, the teams seem to fall naturally into three groups:

  • Above-average Offence and Defence (top right): West Coast, Sydney, GWS, Geelong, Hawthorn, Western Bulldogs. 
  • Above-average Offence but below-average Defence (upper left): Adelaide, Kangaroos, Brisbane Lions, Port Adelaide, Gold Coast (these last two barely above-average on Offence)
  • Below-average Offence and Defence (below left): Fremantle, Richmond, St Kilda, Melbourne, Carlton, Essendon and Collingwood (though their Offence is now only barely below average). 

That first group fills six of the places in the Top 8 on the competition ladder, and the last group fills seven of the bottom 9 places. This makes logical sense (is there another kind?). The teams that seem most out of place are some of those from the middle group, in particular the Kangaroos who currently lie 1st on the ladder, the Brisbane Lions, who sit in 16th, and to a lesser extent the Gold Coast, who lie in 7th.

One of the main jobs of a Rating System is, of course, to adjust past performance for the quality of opposition faced in order to better predict future performance. Usually that will produce some level of divergence between the competition ladder and a Rating System's team ordering. It'll be interesting to see throughout the season how much better MARS, ChiPS and MoSSBODS are at predicting results than is, say, the simple heuristic of choosing the team higher on the competition ladder.

Comparing MoSSBODS' team rankings with MARS' and ChiPS' reveals that it is most divergent for five teams

  • Western Bulldogs, which it ranks 2nd, MARS 4th and ChiPS 7th
  • Hawthorn, which it ranks 5th, MARS 1st and ChiPS 2nd
  • Brisbane Lions, which it ranks 13th, MARS 18th and ChiPS 17th
  • Richmond, which it ranks 15th, MARS 10th and ChiPS 9th
  • Melbourne, which it ranks 17th, MARS 13th and ChiPS 11th

That's an interesting without being disturbing set of differences of opinion, I'd suggest.

To finish, here's this week's Team Rating Weather Vane, now slightly revamped to improve clarity.

From this we can see that seven teams improved both their Offensive and Defensive ratings this week (Roos, Pies, Blues, Cats, Giants, Swans and Dogs) and six saw both these ratings decline (Lions, Power, Dons, Dockers, Saints, Eagles). 

We can also see that Sydney, West Coast, St Kilda, GWS, Collingwood and Essendon had their ratings adjusted most as a result of this week's Scoring Shot performances, while Adelaide, Hawthorn, Fremantle and Carlton had theirs adjusted least.