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This is Foxfooty.com.au’s annual Pythagorean wins prediction piece, which reveals the teams who over- and underperformed in the previous season to predict who’ll bounce back or fall flat in the coming year.

The name makes it sound complicated, but all you need to know is it’s accurate. Of the 15 strongest predictions made by this formula since 2010, 13 were correct.

Of course, one of those incorrect tips came last season, and stood out in black and white.

The core behind Pythagorean wins is figuring out who was lucky and who was unlucky in the previous seasons – determining how many games a team “should” have won – and predicting who’ll rise and fall this season as their luck reverts to the mean.

It’s not purely about performance in close games, which is the simplified way we’ve discussed Collingwood over the last 18 months. It’s about who is playing better or worse than their pure win-loss record suggests, because history says if things get truly out of whack, they’ll fall back the other way the next year.

So, no, this isn’t another column about how incredibly lucky the Magpies were last year. Partly because that didn’t exactly work out for us in 2023. But also because they weren’t even one of the two luckiest teams last year!

WHAT ARE PYTHAGOREAN WINS AND HOW DO THEY WORK?

At the core is a formula, Pythagorean expectation, developed by baseball stats guru Bill James (this is why we used the word Moneyball in the headline – he’s actually relevant to it!). It estimates how many games a team ‘should have’ won based on its scoring. In baseball, this means runs scored and allowed.

This works because looking at a team’s attacking and defensive performances overall, rather than purely whether they won or lost matches, gives us more information.

Let’s go to the extremes. Imagine two AFL clubs. Club A finished 9-1, winning all of its games by one point and losing the other by 100 points. Club B finished 8-2, all of its wins coming by 100 points, its two losses coming by one point.

Which team is better, or more likely to win if they played the next week? The first team won one extra game but its percentage, and arguably its performance, is and was worse than the second team. We’d argue the second team was more impressive; Pythagorean expectation uses the same principle.

There is a core principle at work here: Good teams win games. Great teams win games by a lot.

Using research by footy statistician Tony Corke, we can adapt the formula used to analyse baseball teams to study the AFL.

It doesn’t mean we make a prediction on every team – you need a certain gap between a side’s actual wins and Pythagorean wins (at least 1.5, ideally 2+) for the statistical significance to be meaningful.

Since 2010, if a team had a gap of 2+ games between their actual and Pythagorean wins, the formula accurately predicted if they would rise or fall 19 out of 28 times (67.9%). If the gap was 2.5+ games, the rate improved to 14 of 18 correct predictions (77.8%).

The best modern example of a prediction working out is Brisbane in 2018. They finished in the bottom four with just five wins, but with a percentage of 89.1% – the percentage of an 8.5-win team. They had been unlucky, and Pythagoras thus expected their luck to turn in 2019.

Safe to say it did, because the Lions hosted a qualifying final in 2019.

SO HOW DID PYTHAGORAS’ PREDICTIONS GO LAST YEAR?

Uhh… 50-50?

Collingwood’s remarkable 2022 season, in which they went 11-1 in games decided by two goals or less, made them one of our strongest ever

But one of the many things this formula does not address is personnel. The Magpies, as has been well-discussed, had a brilliant trade period after their preliminary final heartbreak against Sydney, landing a Norm Smith medallist among others.

That, plus the natural growth from impressive young players and career years from veterans like Jordan De Goey, propelled the Magpies to being a much better team and eventually the flag.

So we were right that the Magpies wouldn’t go 11-1 in close games in the home and away season again. They just went 6-1 instead, and then won another three in the finals (partially thanks to Melbourne hating effective inside 50 entries and GWS’ few fans not convincing the umpires of free kicks… the Grand Final shouldn’t have been close, the Pies were quite a bit better). But hey, that means we were technically correct – the best kind of correct.

They clearly played their close-game scenarios extremely well – they have a hell of a lot of recent experience in them. But, in a point we will never stop arguing (even if they go 9-1 in close games again), close game performance is not sustainable year-on-year. History, in all sports, tells us this is the case. Including in footy.

Because Port Adelaide exists. The Power went from 9-0 in close games across the 2020 and 2021 home and away seasons, to 2-7 in 2022, and we strongly expected Ken Hinkley’s side to improve as they bounced back to something closer to average.

Instead, they almost matched Collingwood by going 6-2 in close games across the 2023 home and away season, all of those wins part of their 13-match winning streak from early April to early July. It turned out they weren’t terrible in close games, they were really good, for some reason!