There are three explanations for what happened at the MCG on Friday night.

One – Collingwood had a shocker. It happens, even to reigning premiers – the best medicine is usually to pick yourself up, dust yourself off, and avoid panicking.

Two – Sydney are very, very good. As a rule, consecutive wins over top-four teams from the year before to start a new season is a sign of a bona fide premiership contender, no matter the issues the opposition faces.

And three – and this will be the most concerning for Craig McRae and his coaching department – the Magpies have been comprehensively worked out.

I’d argue it’s really a combination of all three that explains the Pies’ 33-point loss at the ground where they’ve been nigh on unbeatable since McRae took over.

Yes, the black and white ball movement, particularly coming out of defence, was as bad as it has been since the last days of Nathan Buckley. And yes, the Swans were superb, dissecting the reigning premiers in a way ordinary sides will find impossible to replicate. Most teams, after all, don’t have a bevy of speedy, scintillating-kicking on-ballers, a trio of talented tall forwards further afield each with their own set role to play when the footy comes their way, or a master coach in John Longmire pulling the reins.

All the same, there will be concerns. As it stands, the Pies are looking every inch the hunted; and while a lot of teams won’t be able to do to them what Sydney pulled off on Friday night, the good ones – the ones who have had more reason than most to ruthlessly dissect last season’s standard-bearers for weaknesses across the summer – most assuredly will.

It starts in defence, where the Magpies are most obviously vulnerable. It has been McRae’s greatest triumph as coach that a unit featuring one generational superstar in Darcy Moore and a whole bunch of other workmanlike jobbers around him has gelled so cohesively over the last few years so as to become far more than the sum of its parts.

But for two weeks in a row, it has been shredded beyond recognition.

The inside 50 numbers they’re conceding isn’t the problem – GWS had 53 last week, while the Swans mustered 51 on Friday night, nearly bang on their average of a tick under 50 against in 2023.

It’s the marks inside 50 that have ballooned: 13 from the Giants, and a staggering 19 from Sydney. The latter is three more than they conceded in a single match at any point in 2023, and both above their average against of 11.23 last year. You don’t win games of footy with those kind of numbers.

There were two methods the Swans used to rack up the set shots. With the ball in hand, they capitalised fully on both their three-pronged tall forward line of Logan McDonald, Joel Amartey and Hayden McLean, as well as the Magpies’ much-publicised zonal defence that focuses more on where their own defenders are positioned relative to the ball than to a direct opponent.

The below video features a fascinating insight from Luke Hodge as to how this worked:

Note to begin how far behind the Swans’ marking options Darcy Moore sits – everyone knows his modus operandi, of reading the ball in the air better than anyone else and using his superior athleticism to reach wherever it lands and either spoil or mark.

The problem is that a backline featuring a second-gamer in Charlie Dean and a still-rusty Jeremy Howe, with no Nathan Murphy or any other real tall support, isn’t structured to allow Moore to be at his aerial best. And the Swans had the weapons to exploit that.

So as the ball comes in – far shallower and more precise than the Pies have anticipated, hitting the centre corridor some 40 metres out rather than along the boundary – it’s Sydney who dictate. McLean, the biggest of the Swans’ tall trio, is more than powerful enough to legally block Moore’s run, engaging with him near where the ball will fall and deny him the chance to reach the drop with his usual pinpoint timing.

It exposes the young Dean, who has lost all body contact or even sight of his man, Joel Amartey, giving him four metres of space even before the ball has left the Swans kicker’s boot further afield.

With McLean occupying Moore, and Howe busy entangled with Robbie Fox, Amartey has more or less a clean run at the footy, and takes the mark uncontested.

But it’s also worth noting how few Pies were around to support – Howe, Dean and Moore, two of them comfortably outsized in their respective contests, are on an island in the most dangerous space on the field.

That’s where the Swans’ plethora of smaller options have taken their toll: Isaac Quaynor is concerned enough about Isaac Heeney to follow him up to the 50, leaving a paddock of space behind him. Plus, the Swans’ ball movement has been speedy enough to prevent the Pies wingers, Josh Daicos and Steele Sidebottom, from getting back in time to support, even if what they’d have provided aerially would likely have been minimal.

The second method was what they did when it was the Pies with ball in hand – and that was even more spectacular.

From first bounce to last, no Collingwood disposal inside their defensive 50 was safe. It has become a cornerstone of the Swans’ game plan in 2023: they pressure, and harass, and tackle, deeper than just about anyone else, trusting their system behind the ball to press high and savagely.

For two weeks in a row they have scored 45 points exactly from midfield intercepts – some 14 points more than the league average. On Friday night, the Pies’ ball skills wilted in the face of their manic, unrelenting pressure.

By three quarter time, ten of the Swans’ goals had arrived via turnovers; four in the third quarter alone came in their forward half. And when they won the ball back anywhere close to goal, they were deadly.

No team kicks the ball better in those situations than Sydney – a 75 per cent forward half kicking efficiency in the third quarter testament to that – and with the Pies’ desire to take the game on from half-back, there was plentiful space that opened up inside 50 for forwards with a sniff of the goals to run into, and effectively walk it in.

Little wonder four goals to three quarter time came from within 15 metres, with two McDonald majors coming from marks in the square itself.

And it could have been more, too – the Swans butchered a swathe of chances in the first half, this incredible blunder of a two-on-zero situation in the square the funniest of them.

By that point, with the game shot, the Magpies had made 10 unforced defensive half turnovers, and a stack more forced as well. 12 of the 15 goals they conceded came from turnovers as well – seven of them from their back half. Yikes. Yikes, yikes, yikes.

Jack Crisp is far from the first Magpie over the last two years to take the game on from the back half – that’s what they do, after all. Fly’s Pies back themselves to the hilt to bust tackles, create overlap from early on in possession chains, and ride the wave forward.

Except… it’s a high-risk play, and when it fails you look rudderless, especially with a shaky defence as insurance behind it.

Teams will still have to be good enough to capitalise on those opportunities – few teams have the same potent mix of ferocious tackling small forwards, tall targets and beautiful-kicking midfielders to so ruthlessly expose the Magpies’ defensive set-up like Sydney did.

But for those who can… well, there’s now a blueprint set in. Occupy Moore in defence, and use your other options to create an island with your talls to expose Howe and Dean. Move the ball quickly and precisely from turnover, with your forwards poised to sprint back towards goal when it happens. Press high to corral the Pies and deny them the slingshot, fast-paced half-back style they so love.

The Giants exposed them, and now the Swans have too. It’s by no means panic stations, Collingwood fans… but for the first time as coach, McRae finds himself needing to make changes urgently.

The footy world – and those who consider themselves in the premiership window – will be watching on eagerly. The champs have some thinking to do.