Recently I put my AFL leverage simulator through its paces, generating both winning percentages and leverage for the entire 2019 season. The leverage simulator simulates the remainder of each AFL game from any given minute to determine how often a team wins from that point. More importantly, it also determines the game’s leverage, or how much the winning percentage would change if a goal were to be kicked in that given minute.
Combining the play-by-play with the leverage can give an indication of which scoring shots were kicked at the most important points of the match.
There’s a couple caveats here. The most important kick of the season belongs to Michael Walters, whose after-the-siren kick nicked the post to give Fremantle the win over Brisbane after the siren, but would show up 9th in the list if I had included all behinds. The simulator only knows he kicked a goal in that minute, not when in that minute the goal was kicked, so no goal will move the leverage needle a full 100%.
For each minute in each game, the simulator checks to see if any scoring shots were generated, and then simulates the game from there. The leverage gets calculated from two different simulations: the home team’s winning percentage if they were up an additional goal, and the home team’s winning percentage if they were down an additional goal. While I would have liked to write the simulation to use seconds instead of minutes, minutes were functionally practical for two reasons: first, each scoring shot’s time is only estimated, and second, seconds would incrase the length of time a game takes to run from three-four minutes to (does some scratch math) approximately three hours. It might be worth going back and simulating the final two minutes of every close game down to the second, but I have not yet done so. Based on previous simulations looking at close games at the seconds level, would definitely end up changing where goals sit in the rankings. I still consider there to be value in this list as it allows the comparison of late-game goals to other scoring shots, the likely topic of a future blog post.
Also, if multiple scoring shots occurred in the same minute, they have the same leverage – as noted above, the simulator currently works by minute, not by scoring shot. It’s significantly easier this way.
Walters’ scoring shot is a great example of how the simulator works – at the start of the minute that the goal was kicked, with the score locked at 72, Fremantle had an 85.6% chance of winning if they were a goal up with a minute to play, and a 0% chance of winning if they were a goal down. This is a bit low for two reasons. Keep in mind that the simulator treats draws as “no values.” If two teams tie in the simulation, neither of them win and the simulation is discarded. Also, the simulator dramatically underestimates the chance multiple scoring shots will be kicked in the last minute to be effectively zero, so the simulator basically saw no way for Fremantle to win if they were down by six points. In truth, Fremantle would have had a very, very small chance of winning from that point.
Obviously, this will be weighted towards the scores which occurred late in the game as the leverage reached toward its limit of 1. I’ve also removed behinds – the list was full of them, but Walters aside, many of them had no direct impact on the outcome of the game.
Also, all minutes here are, unfortunately, estimated. If you’ve been waiting here thinking, “what about THAT goal?” get in touch and I’ll take a look – noticed some odd things around draws and occasionally when a goal was estimated to be kicked.
And now, to the rankings:
10. Lincoln McCarthy, Brisbane vs Geelong – 75-73, 78th minute – 75.0%
This game winning goal won the battle of 1st and 2nd on the ladder at the Gabba, though it left enough time on the clock for Esava Ratugolea to get a point back.
9. Shaun McKernan, Essendon vs GWS – 71-71, 77th minute – 75.6%
McKernan tied the game for the Bombers – a GWS goal would have won the game for them, but instead turned the game into a 50-50 contest. The highest ranked goal which didn’t directly win a game. If you forgot who won, hang on, you’ll remember shortly.
8. Michael Walters, Fremantle at Collingwood – 79-75, 80th minute – 77.4%
Walters’ goal clinched victory for Fremantle at the MCG – Fremantle weren’t given much of a chance to win this game (19%) and as such the simulator thought Collingwood very likely to kick an additional goal, lowering the leverage a bit. Another game where a by-second simulation would increase the percentage a bit.
7. Anthony McDonald-Tipungwuti, Essendon vs North Melbourne – 86-81, 80th minute – 83.1%
Up 18 at three-quarter time, Essendon gave up 21 straight points to the ‘Roos but McDonald-Tipungwuti’s goal clinched the win.
6. Marty Hore, Melbourne at Gold Coast, May 11 – 60-60, 80th minute – 83.3%
Tom McDonald’s behind won the match, but Marty Hore’s game-tying goal happened at a crucial juncture of the match. This missed the top three mostly because Melbourne were expected to beat the Suns by a greater margin, so the simulator assumed the favourites would kick goals more often.
5. Josh Bruce, St Kilda vs Fremantle – 72-69, 80th minute – 83.6%
Bruce’s game winner came with 42 seconds left.
4. Jack Bowes, Gold Coast vs Carlton, April 14 – 59-57, 80th minute – 84.0%
Bowes scored with 13 seconds left on the game clock to lead Gold Coast over the Blues, so again the actual leverage of this kick was closer to probably 99.8% – but still shows up as hugely important in the rankings.
3. Eddie Betts, Adelaide at Brisbane, May 18 – 92-93, 80th minute – 84.8%
Betts scored with about three seconds left in the game, so the leverage here assumes there was time to kick another scoring shot – there wasn’t. The leverage here is a little higher than Bowes because of the one-point margin at the start of the last minute. If the simulator looked at seconds instead of minutes, I’m nearly certain Eddie wouldn’t make the list at all.
2. Cale Hooker, Essendon vs GWS – 77-71, 80th minute – 86.3%
Hooker’s kick won Essendon the match in spite of the odds (well, Essendon’s winning percentage was about 49% at that point.) I had to manually add this kick to the top of the list due to a double issue with how the game was coded, and what the simulator assumes with the game being tied if GWS were to be given a goal (considering it knocks out drawn games.)
1. Marc Murphy, Carlton at Fremantle, June 30 – 79-75, 80th minute – 87.4%
Marc Murphy didn’t kick after the siren, but his very late goal put Carlton up by 4 with only a few seconds left to play to cap off the upset – Fremantle were given a 78% chance of winning by the pundits.
And of course, a special additional mention for Michael Walters, who really should be all the way down here with that after-the-siren behind.