What does winning in round 1 mean?

HPN has previously established that the predictive powers of the preseason are minimal at best, but after yet another crazy week of football to open up the season but we thought it’d be useful to look at how telling the first round of results would be in determining the make-up of the finals.

HPN has looked at the round one results of the last decade, and compared them to the eventual finals make up. We have considered two classes of results: eventual finalists beaten in round one by teams who missed the finals, and eventual finalists beaten by other finalists who finished lower down the ladder.

For example, Melbourne beating GWS (remember that everyone?) last year was an example of a non-finals team beating a finals team, whereas North beating Adelaide last year was an example of a lower ranked finals team beating a higher ranked one.

Finals teams losing to non-finals teams

2007-2016 FinalsNonFinals

Each season there are about 4.6 matchups between finalist and non-finalist sides (either four or six each year). Of those matchups, the underdog wins one a year on average – or 23% of the time. Think of the aforementioned Melbourne win, or GWS beating Sydney in 2014.

Lower ranked finals teams beating higher ranked finals teams

2007-2016 FinalsLowerFinals

Likewise, each season in the last decade has seen between one and two matchups between eventual finalists, with the team that turned out worse (according to the full home and away season’s results) winning 41% of the time.

What does this mean?

Essentially, it means that, like all weeks of football, results differ from both expectations but also final season outcomes for all sorts of reasons. Some teams may take pre-season easier than others, and come into round one underdone. Teams who go deep into September last year have had a delayed preseason and this may cause poorer early performance. Others, such as North Melbourne last year, can peak quite early in the year before fading away. Some teams may be trialling new tactics or structures and suffer from the lack of familiarity. Injuries can take different tolls at different points in the season.

The upshot is that one week of football isn’t enough to show the relational strengths of the entire league, and predicting finalists from such a small sample is obviously fraught with risk. Instead, we’re big fans of the shifting probabilities approach by Matt Cowgill of The Arc and ESPN

Ignoring the sentence above, how can the data above potentially apply to the 2017 season?

Using our HPN ladder predictions from last week, we can have a guess to apply last week’s results to this season’s round one performance.

2017PythagLadder

The games which will turn out to have been upsets (by an eventual non-finalist or by a weaker finalist) have no immediate candidates in this view. No side from inside the HPN predicted ladder top-8 was beaten by a side outside of it. The biggest HPN win-differential upsets were Essendon (6.4 wins) over Hawthorn (9 wins), and Port Adelaide (13.7 wins) over Sydney (17.3 wins).

We recognise that we’re probably differing from the prevailing consensus here in rating Hawthorn lower and Port Adelaide higher, and it’s perfectly possible these will still look like big upsets in four months’ time.

It is the Port Adelaide win that looks most to us like an upset between two finals-bound teams, along with the Adelaide (17.2 wins) victory over GWS (17.4 wins) which was surprising only in its nature and margin.

If our preseason projections above turn out to be accurate, then this season has had a pretty typical round one as far as results go. The Dogs, Melbourne, West Coast and Geelong would all turn out to have beaten future non-finalists, with no upsets. Hawthorn and Essendon would eventuate as a matchup of non-finalists. With GWS and Sydney being upset by Adelaide and Port respectively, both match-ups of predicted finals sides would turn out to have been upsets.

If Hawthorn or St Kilda (for instance) make the finals or Port Adelaide or Melbourne don’t, then in hindsight we’ll have had more upsets. If Essendon make the finals or Sydney don’t, then we’ve instead had a taste of things to come for those teams.

We’ll see in several months if this stupid prediction will work out.

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