What Makes Finals Different from Games in the Home and Away Season?

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This week we’ll be entering what promises to be one of the most closely-contested Finals series in recent years. If you believe the bookmakers’ assessments, each of the top four teams have at least a 15% chance of snaring the Flag, and Adelaide and West Coast both have chances of around half that.

What effects do the heightened consequences of victory and defeat have on the way that Finals are played, and how do these show up in the scoring and the results?

In today’s piece we’ll be drawing comparisons between Finals and regular home and away season games across the entirety of VFL/AFL history. 

Because relatively few Finals are played each season, to make the comparisons more meaningful in a statistical sense we’ll group seasons into eras – six of them, each including between 15 and 25 individual seasons. Using these groupings, as shown in the table, we end up with at least 75 Finals in every era, which should be enough to provide some reliability to our analyses.

Victory Margins, Scoring and Accuracy

Finals tend to pit more evenly-matched teams against one another, so it’s not entirely surprising to find that, across history, victory margins have tended to be larger in home and away games than in Finals from the same era.

In the modern era, which we’ve defined as the period since 2000, the average victory margin in Finals has been about 2.5 points lower than in home and away season games (33.4 v 36.0 points).

What’s also apparent from this chart is the overall reduction in the size of a typical victory in the 2000-2015 period compared to 1980-1999, both in Finals and in home and away season games. A typical victory margin in home and away game in the 1980-1999 era was 37.5 points, and a win in a Final 36.8 points.

The reduction in the average victory margin has come with a similar reduction in the prevalence of “blowout” victories, defined here as wins by more than 10 goals.

In the 2000-2015 era only about 19% of all home and away games and 15% of Finals have been a blowout under this definition. That’s down from 19% and 21% respectively in the 1980-1999 era. Earlier eras, in which scoring generally was lower, saw very few victory margins of over 10 goals.

Smaller victory margins and generally fewer blowouts in Finals compared to home and away games have come with less total scoring in Finals, too.

Whilst this has been true in every era, the gap has been largest in the most recent era where Finals have, on average, produced about 2 goals fewer than a typical home and away season game (175 vs 187 points). In the previous two eras, by comparison, the gaps were only about 3 points in 1980-1999 (196.1 vs 199.4) and less than half a point in 1960-1979 (175.3 vs 175.6).

Some of that larger difference for the most recent era can be attributed to the smaller number of scoring shots that have been generated in Finals (48.7 v 50.9), but some of it also comes down to the fact that teams have been generally less accurate in converting those scoring shots into goals in Finals than they have been in home and away games (51.9% v 53.6%).

This reduction in accuracy could plausibly be the result of the pressure of Finals football affecting teams’ accuracy for even relatively simple set-shots, but it might also stem from an increase in the average difficulty of shots created in Finals compared to those created in home and away games. Put simply, you’re probably less likely to have a shot from 25m out straight in front in a Preliminary Final in September than you are in a Round 1 game in March.

Previous analyses have shown that teams with strong offences facing teams with weak defences will tend to generate better quality scoring opportunities and hence will be more accurate. The fact that we’ll see more games with this sort of mismatched offensive and defensive strengths during the home and away season than we will during the Finals might be what ramps up the average difficulty of shots in this latter part of the season and drags down accuracy.

One way of attempting to control for the overall greater variability in opposing teams’ abilities in the home and away season is to look only at home and away season games played between teams that subsequently made the Finals.

If we do that we find that there is only a fractional reduction in the size of the gap between accuracy in Finals and accuracy in the home and away season in the modern era. In games pitting finalist v finalist in the home and away seasons of 2000 to 2015, the average accuracy was 53.4%, which is only 0.1% lower than the accuracy for all home and away games during that period.

So, we’re still left with about a 1.6% difference in the accuracy of finalists when they meet in the Finals compared to when they met in the home and away season.

Some of that difference might be explained by differences in where or when the games were played – teams, for example, are much more accurate at Docklands than at the MCG, and slightly more accurate in day games than in afternoon and night games – but pressure remains a plausible explanation for at least some of this difference. It might also be the case that teams play a more defensive style in Finals so that even when the same two teams meet, the average quality of scoring opportunity reduces in Finals.

 

Before we move on let’s briefly review the team-by-team data on accuracy in home and away games compared to accuracy in Finals for the modern era, bearing in mind that a number of teams have played relatively few Finals during this period, which makes their overall accuracy subject to large sample variation. (The numbers appearing above each bar represent the number of games played by that team of that type.)

We see that every team except Melbourne, North Melbourne and Richmond have exhibited the general pattern of being more accurate in the home and away season than in the Finals, though for most teams the differences are quite small – less than the all-team 1.6% figure.

For five teams, however the differences are larger:
•    Western Bulldogs: 7.0% (47.8% vs 54.8%) – 13 finals
•    West Coast: 4.3% (49.5% vs 53.8%) – 20 finals
•    Geelong: 3.0% (50.9% vs 53.9%) – 27 finals
•    Fremantle: 2.9% (50.4% vs 53.3%) – 15 finals
•    St Kilda: 2.3% (52.2% vs 54.5%) – 17 finals

One notable feature of four of these five teams is that their home and away season accuracy is above the all-team average of 53.6%, and their Finals accuracy is below the all-team average of 51.9%. St Kilda is the only exception.

Upsets and Form

Since, as we’ve noted a few times now, Finals tend to pit teams of more equal ability against one another, it seems plausible that we might see more upsets in Finals than in home and away games (where we’ll define an “upset” as a win by the team assessed, pre-game, as being less likely to win according to a fairly simple team rating system ).

That has, indeed, been the case in every era except the most recent one where favourites have lost about equal proportions of home and away games and of Finals (viz 30%).

That proportion has remained fairly constant for home and away games across the last few eras, but has fallen dramatically in Finals from a figure of over 40% in 1960-1979, to about 35% in 1980-1999 before reaching its current 30%.

What’s especially interesting about the modern era, however, is how much more likely it is that there will have been upset results in games involving the subsequent finalists when they met earlier in the season.

In excess of 40% of these games resulted in the less-highly rated team emerging victorious.
Clearly, the motivation of Finals and the style of football that is played in them is enough to materially enhance the prospects of the stronger team, however small might be its superiority.

What this implies, of course, is that home season results in games played between finalists might not necessarily be a good guide to Finals.

To explore this issue let’s look just at Qualifying and Elimination Finals and use the following simple rule:

  • In the Final, select the team who won the corresponding encounter in the home and away season
  • If the teams met twice in the home and away season and won one each, use the aggregate score across the two games to make the prediction

Employing that approach for the 64 Finals across the 2000 to 2015 period would have yielded a paltry 57% record, in some seasons getting as many as three of the four results incorrect. Only once, in 2011, would it have resulted in a four from four performance.

Summary

If we look just at the modern era of football from 2000 to 2015, we find that, compared to a typical home and away game, a Final will typically:

  • have a smaller victory margin and be less likely to be a blowout
  • produce fewer scoring shots
  • see lower accuracy in terms of goals as a proportion of scoring shots
  • be less likely to produce an upset (compared to games played between finalists during the home and away season)