Even though only my extreme partisanship completely explains why, I greatly enjoyed the first live footy match I watched in 2019.
Most neutrals – if they were watching at all – had turned off the North Melbourne-Carlton game after watching the Kangas kick the opening seven goals to lead 10.6.66 to 1.7.13 at halftime. We stayed around the entire second half just because we found the game severely enjoyable. However, the game was long over, with only the first goal of the second half, scored by Jack Silvagni to get the Blues back within 9 goals, registering at all on the leverage calculation.
While a close AFL game is as exciting as any sport in the world, I’m still curious to know: when are AFL games won or lost?
Thinking specifically about “when are games won?” may conjure up the West Coast-Port Adelaide after-the-siren final a couple years ago in your mind, or the 2018 Grand Final where the game was again won late by West Coast.
The North-Carlton game, however, was won at some point in the first quarter.
One of my favourite infographics from Matter of Stats, Types of Grand Finals, looks at grand final outcomes by quarter scores and demonstrates this isn’t an obvious question. Most grand finals end up with one team winning start to finish – even a game between two of the best teams on the biggest stage of the season doesn’t mean the game itself will be all that good, one of my working hypotheses throughout these blog posts.
However, I wanted to take this a step further with the concept of leverage. While there’s nothing wrong with looking at games based on their quarter time score, calculating leverage gives us 20 times the amount of data points, and includes initial winning percentage in the calculation.
Leverage, as I define it, is a percentage which reflects how much the game’s winning percentage would change if either team kicked a goal in that minute. The closer the game, the more evenly the teams matched, the higher the leverage will be. For instance, in the 2018 grand final, the leverage with one minute to play rose close to 100%, whereas in the 2019 grand final the leverage was functionally 0% for the entire second half as Richmond’s winning percentage was close to 100% and GWS didn’t launch any sort of comeback.
Therefore, leverage can be used to determine at which points AFL games get won or lost. The 2018 grand final was won in the final minutes, whereas the 2019 grand final was arguably won in the second quarter.
I’ve gone ahead and categorised the different types of games which the 2019 season gave us. It won’t add up to 207 – I noticed an error I made typing in winning percentages for three of the finals games (switched home and away) and haven’t re-run them yet – but that won’t make a difference for this blog post. I’ve done this by taking the average leverage for each quarter instead of looking at who’s winning at quarter time.
For instance, the Carlton-North Melbourne game where North played a wonderful first quarter featured an average leverage in the first quarter of 10.8%, second quarter of 3.1%, and third quarter of 0.3%, and a fourth quarter where no score changed North’s 100% winning percentage. The most exciting game of the season by this metric, the Fremantle-Sydney game, featured a Q1 of 17.0%, Q2 of 19.0%, Q3 of 23.5%, and a fourth quarter average leverage of 44.8%, in part because the one-point game was so close the leverage line trended towards 100% by the end of the game.
For our purposes, in the first instance, North “won” the game in the first quarter, since that quarter had the highest average leverage. The Freo-Sydney game came down to the wire, making the fourth quarter the time when the game was “won”.
I’m specifically curious about this in part because of my above hypothesis, as a grand final is more likely to be dull than not – and also for predictive analytics. Predicting large wins could have uses in both gambling and modeling. We typically associate winning percentage with average margin, to the point where the leverage simulator even uses this to translate how many goals each team will score given a starting winning percentage based on Sqiggle. I kind of want to know if we can figure out the odds of a specific game being horrifically dull.
So, without further ado, the most likely leverage patterns in 2019 AFL games. The numbers represent quarters – the first number on the left is the quarter with the highest rank, the last number on the right represents the quarter with the lowest leverage.
The 5 most common types of AFL games
1234 – The early blowout – 42 instances
You were more likely to see an 2019 AFL game end in a blowout where the first quarter was the most interesting than any other type of game. None of these games rate very highly on the intrigue scale, and the majority of them were straight blowouts – though this category does include games such as the GWS-Footscray final where the first quarter was close all the way through, the second and third quarters weren’t as close but the game wasn’t over, and the fourth quarter was functionally predetermined. None of the games in this category featured interesting final quarters.
Most interesting game: May 19, Hawthorn-Richmond (117th most interesting)
Least interesting game: May 19, Carlton-GWS (dullest game of the year)
Most games played in this category: 8, GWS and Gold Coast
Fewest games played in this category: 2, St. Kilda and Sydney
4321 – The closest of games – 36 instances
9 of the top 10 “most interesting” games fall into this category since leverage is higher in the fourth quarter. These games were close almost all the way through – even some of the games which got away, like the Footscray-Geelong game on July 6th, were close for almost the entire game.
Most interesting game: July 20, Fremantle-Sydney (most interesting game of the year)
Least interesting game: July 6, Footscray-Geelong (75th most interesting)
Most games played in this category: 7, Melbourne and Essendon
Fewest games played in this category: 2, Adelaide, Footscray, Wst Coast, Richmond, Hawthorn
2134 – The second-quarter blowout – 30 instances
Similar to the early blowout, almost none of these games had interesting second halves, but the winning team didn’t quite pull away as quickly as they could have. A perfect example is the Richmond-Brisbane game the first week of finals where Richmond increased their winning percentage from the 30% range all the way up to 80% by the end of the second quarter. Many of these games have very similar leverages between the first and second quarters, implying the first quarter was either fairly even or the underdog stayed in the game. Some of these games even had fairly interesting third quarters, but whoever was in front always pulled away.
Most interesting game: July 20, Carlton-Gold Coast (100th most interesting game of the year)
Least interesting game: August 10, Port Adelaide-Sydney (161st least interesting game of the year)
Most games played in this category: 7, Richmond (Port and Essendon had 5)
Fewest games played in this category: 1, North Melbourne
3214 – the third-quarter pull-away – 26 instances
Yes, more games with boring fourth quarters, though these games were a bit more exciting generally. These games have stayed close until the third quarter until one team ends up running away with it – the Brisbane-Melbourne game is a perfect example of this, with Brisbane starting the quarter six points behind and finishing the quarter with a 14-point lead after kicking 6.2 to 3.1, and then piling on in the final term. These games can even have what appear to be exciting fourth quarters ahead – for instance, the Hawthorn-North Melbourne game where the Hawks were ahead by a point entering the final quarter and then kicked five of the next six goals had a fairly decent leverage score in the 4th quarter.
Most interesting game: April 7, Hawthorn-North Melbourne (61st overall)
Least interesting game: July 13, Geelong-St. Kilda (136th overall)
Most games played in this category: 6, St. Kilda
Fewest games played in this category: 0, Carlton (Essendon and Gold Coast on 1)
4312 – the boring second quarter – 10 instances
A very interesting category! Consider the Carlton-Fremantle game, where Freo were up 29 after the first quarter, 10 at halftime, and lost by 4 – doesn’t seem like it would be a candidate to have a lower leverage second quarter, but the simulator had Fremantle as fairly heavy favourites at 78%, which meant their win percentage at Q1 time was greater than 90% – the Blues’ second-quarter mini- comeback only got the win percentage back to about 85% down 10 at halftime. Or the Collingwood-Footscray game from April where both teams had a relatively quiet first half – the score at Q1 time was 1.2.8 to 0.3.3, and the Magpies’ lead remained between five and 17 points the entire second quarter. The game was close late until Collingwood broke the game open about halfway through the fourth quarter. There really wasn’t much difference between the Q1 and Q2 leverage in this game, but the fairly even scoreline and the favourite slowly staying ahead meant the Q2 leverage was a bit lower than the Q1 leverage.
Most interesting game: June 29, Hawthorn-West Coast (8th overall)
Least interesting game: June 30, Carlton-Fremantle (79th – a bit low, but consider the game wasn’t close until late)
Most games played in this category: 4, Collingwood (3 each for Fremantle and Carlton)
Least games played in this category: Six teams avoided this entirely (Melbourne, Adelaide, Gold Coast, GWS, and Port Adelaide.)
The 16 other types of AFL games (which occurred in 2019)
The 2314 – 9 instances – decently entertaining games with generally uninteresting final quarters, either the losing team kept the game close enough in the third to stage a comeback, or the underdog ended up with a blowout.
The 1324 – 8 instances – whoever is getting blown out gets blown out quickly but shows just a glimmer of life in the 3rd quarter (June 8, North Melbourne-Gold Coast, in part due to a late Gold Coast second quarter run, meaning if they had kept it up in the third the game would have been a toss-up.)
The 4213 – 7 instances – exceptional games, as the fourth quarter’s quite exciting but the third quarter isn’t. Think St Kilda-Hawthorn where the underdog comes back to win in the final quarter. The favourite/team in the lead at halftime has a good third quarter so the leverage lowers, and winning percentage assumes the team in the lead will go on and win, so these games aren’t rated very highly compared to the games which are close throughout – but these are games you’d like to watch no matter which team you support.
The 3241 – 7 instances – These games weren’t evenly matched but stay close until the late third or fourth quarter – not dissimilar to 4321s with a tight first half but where the fourth quarter isn’t close.
The 3412 – 6 instances, and the 3421 – 6 instances
Functionally equivalent instances such as the Carlton-Footscray game from June where the underdog has a big third quarter after a quiet first half, or the Geelong-West Coast final where the underdog has a big third quarter after a quiet first half, or the North Melbourne-Adelaide game where the teams were roughly equal but North came back to win with a big third quarter, or the Adelaide-Geelong game from April where Adelaide lost by four goals but had a big third quarter – sensing a pattern yet? The “big third quarter” game, typically by the team who was no longer favoured to win at half-time.
The 3124 – 4 instances – think that Richmond-GWS game from July where the teams were evenly matched, Richmond jumps to a 31-point lead in the mid-second quarter, GWS get back within 10 in the 3rd, and then Richmond close the game out. Seemingly involves only Richmond or Fremantle (2 games each.) Yawn.
The 1243 – 4 instances – the team getting blown out maybe gets a couple goals in the 4th. Yawn.
The 4132 and 4123 – 2 instances each – Round 1. Footscray-Sydney. Footscray are up 32 and win by 17, but not before Sydney got within 4 with only a few minutes to play. Melbourne are up 30 on Carlton at Q3 time. Carlton storm back, take the lead at 99-98, then still lose. The Collingwood-West Coast rematch where Collingwood, down 16, kick 2.6 to 0.1 in the final quarter to win. In short, the big 4th quarter comebacks.
The 2143 – 2 instances – These were both comebacks (Adelaide-Richmond in June and Footscray-Hawthorn in March.)
The 2341 – 2 instances – One blowout and one game where the losing team made a run in the second quarter but lost decisively.
The 4231 – 1 instance – the Brisbane-GWS final had a slightly more interesting 2nd quarter.
The 3142 – 1 instance – this was the Richmond-Carlton season opener. The leverage was always so low throughout the entire game, the result is effectively just noise.
The 1432 – 1 instance – Gold Coast won the second half against West Coast. They still lost by 23.
The 1324 – 1 instance – That West Coast-Fremantle game where Freo never came close to leading but still got within 10 points in the 3rd.
You may have realised there are 24 possible outcomes (4x3x2x1 = 24) and I’ve only given you 21 – the three outcomes which didn’t appear in 2019 were the 1423, the 2413, and the 2431. These should all be rare occurrences where a team which will be blown out nevertheless makes just a bit of a run in the fourth quarter.
Conclusions
The pure number of games which aren’t ultimately close in AFL strikes me more than anything. Leverage should naturally be highest in the fourth quarter, as a goal in a close game will have a large impact on the game percentage. The top 366 individual scoring plays by leverage all occurred in the 4th quarter (out of 9265 outcomes, including rushed behinds.) The individual scoring plays give us a sense of the maximum leverage by quarter – the individual scoring plays with the highest leverage were 100% in the 4th quarter (after the siren for the win), 32% in the 3rd quarter, 23.4% in the 2nd quarter, and 20.4% in the 1st quarter.
However, the 4th quarter in 2019 had the highest leverage only 25.1% of the time, meaning only one in four games has a relatively close final outcome. The third quarter had the highest leverage 58 times, the first quarter 56, the fourth quarter 52 and the second quarter 41.
Switching things around, in spite of its built-in advantage, the fourth quarter had the lowest leverage 119 times out of 207, or 57.5% of the time!
There’s a point in every AFL game, and probably every timed sporting event, where the lead becomes unassailable. By the time the final goal of the Carlton-Collingwood game had been kicked in May, a Will Hoskin-Elliott goal which put the Magpies up by 3.1 with practically no time left, even a Carlton goal would not have changed the game’s outcome.
To calculate this, I looked at the point where the leverage remained zero – i.e., there was a less than 1-in-10,000 chance the losing team would come back to win. I’ve also looked at where the leverage was less than 1%, which should indicate a point in the game where the losing team’s pretty much cooked but still has a chance to come back.
This point tends to happen at some point during the 4th quarter.
There were 50 games where the leverage in the final minute was greater than zero. In 16 of those, a comeback was unlikely (needing two scores to win.) In 34 of those games, the leverage reached above 75%, meaning the game was functionally within a goal. This means there’s about a 1-in-4 chance an AFL game will be decided in the final two minutes.
There’s about a 1-in-21 chance the game will be entirely over before the 4th quarter, but when looking at games where comebacks are unlikely, this rises to almost 19% of all matches. Half of all matches have a sure winner with five minutes to go.
Understanding how games work may have its largest use in betting and predictor markets. The Squiggle average winning percentage for favourites in the 2019 season was 64.8%, which my simulator predicts as a roughly 10-point favourite, or less than two goals. It may be interesting for those creating models to try and predict how the game will be won as opposed to just looking at the likely margins.