2021 : Simulating the Finals before Week 1

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Today we take a first look at a MoSHBODS-based simulation of the nine games of the Finals.

METHODOLOGY

Broadly speaking, the simulations of the Finals will use the same methodology that was used in the simulations of the home-and-away season, including the manner in which home ground advantage is estimated.

Home Ground Advantage or, in MoSHBODS’ terms, Venue Performance Values (VPVs), are handled a little differently in Finals than they are in home-and-away games in that multipliers are applied to them as follows

  • In Finals other than the Grand Final played in a team’s home state, the same VPVs are used as would have been the case if the game were played in the home-and-away season

  • In Finals other than the Grand Final played in other than a team’s home state, the VPVs are doubled

  • In Grand Finals, the VPVs are multiplied by 0.25

Those multipliers have been determined by reviewing the historical record, but you could certainly argue whether or not they should apply in a season like this one, and you could equally argue that the number of Finals that have been played in an era where interstate clashes were possible is relatively small. Nonetheless, as is MoS custom, we will use the methodology that was determined pre-season and review its efficacy and consider changes post-season.

Now, to implement the approach, we do need to make some assumptions about where the Semi-finals, Preliminary Finals, and Grand Final will be played, contingent on whose playing in them. The assumptions used for the simulations are as follows:

  • Semi-Final 1 will be played at the Gabba if Brisbane are in it and at York Park otherwise

  • Semi-Final 2 will be played at Kardinia Park if Geelong are in it, and at Adelaide Oval otherwise

  • Preliminary Final 1 will be played at the Gabba if Brisbane are in it and at the MCG otherwise

  • Preliminary Final 2 will be played at the Adelaide Oval if Port Adelaide are in it, at Kardinia Park if Geelong are in it, and at the MCG otherwise

  • The Grand Final will be played at the Adelaide Oval

Those assumptions, too, are debatable, I acknowledge, but computer algorithms need inputs, and these are certainly inputs.

RESULTS

In this first chart we simply look at the estimated probabilities for each of the 8 Finalists going out in a particular week of the Finals.

The simulations very much value the double-chance and we see that the Top 4 teams provide the Grand Finalists in all but a small number of replicates, with the Bulldogs the only team from outside the Top 4 registering a probability above 5% of making the final game of the season.

We also see that Melbourne is rated about a 3-in-10 chance for the Flag, Port Adelaide 1-in-4, and Brisbane Lions and Geelong about 1-in-5 chances

Drilling down a level on the 50,000 replicates, we can analyse the paths to elimination followed by each team, and these are summarised in the chart below.

We see, for example, that Brisbane Lions:

  • goes out in a Semi-Final to the Western Bulldogs in about 4% of replicates and to Essendon in another roughly 2.5%

  • goes out in a Preliminary Final to Port Adelaide in about 12% of replicates, to Geelong in about 9% of replicates, to Sydney in about 0.5% of replicates, and to GWS in about 0.2% of replicates

  • loses in the Grand Final in about 20% of replicates

  • wins the Grand Final in about the same proportion of replicates

Lastly, let’s look at what the replicates reveal about possible Grand Final matchups.

We see that a Port Adelaide v Melbourne Grand Final is the most common pairing, accounting for about 18% of all replicates. Melbourne wins about 60% of the time.

Next most-common is a Melbourne v Brisbane Lions Grand Final, which also appears in about 18% of all replicates, with Melbourne winning about 57% of them.

Geelong v Port Adelaide accounts for another 17.5% of replicates, and Geelong v Melbourne another12.4%.

Altogether, Grand Finals involving any two of the Top 4 teams account for about 87% of all Flag winners.