2012 MARS, Colley, Massey and ODM Ratings After Round 17

MARS was once again the Rating System making the fewest re-rankings this week, but still found reason to reshuffle one third of the teams, all of them from amongst the top 8. Of the six teams to move on MARS, only two moved by more than a single spot: Adelaide, climbing two spots to 6th, and West Coast, falling two spots to 7th.

Two of the teams that did not change their Ranking this week were Geelong in 4th and Port Adelaide in 15th, the Ratings gap between which defines our interquartile RP metric, a rough measure of the relative strengths of the top and bottom sections of the ladder. While both teams were net RP gainers in the round, Geelong's gain of 5.2 was much larger than Port's gain of 2.5, so the interquartile RP range grew by 2.7 RPs this week to a season high 56.3 RPs. Another indicator of the gap between this season's haves and have-nots is the fact that we now have 10 teams with MARS Ratings comfortably above 1,000.

Four teams now occupy a position on MARS Ratings that is 3 or more places different from its position on the competition ladder. Geelong are 4th on MARS but 7th on the ladder, St Kilda are 5th on MARS but 10th on the ladder, Adelaide are 6th on MARS but 2nd on the ladder, and Fremantle are 12th on MARS but 9th on the ladder.

This week's table of recent MARS form spans six games for each team rather than five, a situation necessitated by the short rounds 11, 12 and 13 during which each team played two games and which make it impossible to select an earlier round number after which all teams have played exactly five games.

Across those six games, the Hawks, Roos, Swans, Crows and Dockers have accumulated most Ratings Points (RPs), each adding between about 7 and 18 RPs to the tallies they had at the end of Round 10. The Lions, Saints and Cats are the only other teams to have added RPs across that period, each grabbing between about 2 and 4 RPs.

During this same period, the Dogs, Port, Tigers, Dees, GWS have been the largest RP contributors, each surrendering between about 7 and 15 RPs to their opponents. The next four most generous contributors, West Coast, Carlton, Collingwood and Essendon, are all.more surprisingly, teams still harbouring hopes for a spot in the Finals come September.

Gold Coast is the only other team to have shed RPs over its last six games, though its loss of just over a single Point seems relatively respectable in light of the much larger losses by teams more fancied than the Suns. It's also, of course, an indication that the Suns have been playing to their Rating of around 940-945 RPs.

Amongst the other Rating Systems, Massey was the System re-ranking the greatest number of teams. It altered its opinion of 10 teams this past week, including three teams by more than a single spot: Carlton from 8th to 10th, Essendon from 5th to 7th, and Geelong from 11th to 8th.

Colley and ODM each made seven changes, though only two of Colley's were by more than a single spot: Adelaide from 3rd to 1st, and Collingwood from 1st to 4th. In contrast, amongst ODM's seven changes were six by two spots or more: Collingwood and Essendon swapping 7th and 5th, St Kilda and West Coast swapping 6th and 4th, Richmond moving from 9th to 11th, and Geelong rising from 11th to 8th.

Looking across the four Ratings Systems, five teams are now ranked significantly differently by them: 

• Adelaide, ranked 1st by Colley, 3rd by Massey and ODM, and 6th by MARS
• Fremantle, ranked 8th by Colley, and 12th by all three other Systems
• Geelong, ranked 4th by MARS, 7th by Colley, and 8th by Massey and ODM
• St Kilda, ranked 4th by ODM, 5th by MARS, 6th by Massey, and 11th by Colley
• West Coast, ranked 4th by Massey, 5th by Colley, 6th by ODM, and 7th by MARS

ODM then has quite different opinions about the merits of a number of teams. One of the charms of ODM is its willingness to deconstruct its opinions about each team into an offensive and a defensive component.

Generally, its ranking of each team on their offensive merits is similar to its ranking of that same team on their defensive merits, the obvious exceptions being Fremantle, ranked 3rd defensively and 12th offensively (and 12th overall); the Roos, ranked 15th defensively and 2nd offensively (and 10th overall); St Kilda, ranked 11th defensively and 4th offensively (and 4th overall); and Sydney, ranked 1st defensively and 6th offensively (and 2nd overall).

Currently for ODM, overall rankings are slightly more correlated with offensive rankings than they are with defensive rankings. The respective Spearman rank correlations are +0.79 for defensive rankings and overall rankings, and +0.90 for offensive rankings and overall rankings.

Lastly, using the Rating Systems to predict Round 17 results - selecting the team with the higher Ratings as the likely victor - MARS would have selected 8 correct results, while Colley, Massey and ODM would have each selected only 7. Commencing with this strategy from Round 5 of the season, that moves MARS now one tip ahead of Colley, two ahead of ODM, and four ahead of Massey.