It's the penultimate weekend of the football season, and time for those most fraught of games — the AFL preliminary finals.

Sydney, Port Adelaide, Geelong and Brisbane cannot worry about the flag this weekend.

For these four teams, there are no second chances. They have to get it right or miss out on the grand final.

On one level, these are one-off games of football where both sides start with 0 points on the scoreboard.

On another, there are trends through the season and recent history that can be used to view these contests.

So what are the keys to these two finals? Will it be personnel, tactics, mindset, location, or a mix of the lot?

Sydney vs Port Adelaide

Will history repeat itself for the Swans?

We talk about football being a mental game as well as a physical one, and the opening match of prelim final weekend shows exactly why.

The Sydney Swans have lost eight straight against Port Adelaide by an average of 34 points — although it's weighted heavily by the most recent one, when Sydney was crushed by 112 points at Adelaide Oval in round 21.

More pertinently for Friday night, that run includes the past three times the two sides have met at the SCG.

The question is whether Port Adelaide's game style is better suited than most against Sydney, or whether they have got in the Swans' heads to some extent.

That last thrashing was surely an outlier, where the Power scored 90 points from intercepts and 57 from clearances in a dominant display.

At that point, Sydney had lost five games out of six — since then, however, they have won four in a row including a thriller against GWS in the qualifying final.

On the other hand, the Power were being written off after an 84-point thumping by Geelong in week one of finals. But now they're in a prelim.

So which version of each team turns up, and if it's close, will it be a case of history repeating?

Rioli the linchpin for the Power

There are plenty of important players for Port Adelaide, from stars Zak Butters and Connor Rozee to Jase Burgoyne, who was brilliant off half-back a week ago in the semifinal.

But the most important of all might just be Willie Rioli.

Rioli has speed, awareness and a lot of skill, which have all been on display in the last few weeks.

The former Eagle small forward has kicked eight goals and had five goal assists in the last month of football, not to mention four majors in the round 21 game.

He was superb against Hawthorn in last week's semifinal, kicking two goals and setting up numerous attacks with his pinpoint kicking and passing.

He will be much needed on the tighter spaces of the SCG.

Stop Heeney, stop Sydney? Not quite, but it's a start

There's a tendency when we look at star players to think that shutting them down is the be-all and end-all to winning a game.

Opposition clubs looking at Sydney's Isaac Heeney could well have that feeling seeing how he has gone in the late part of the season. He has been pivotal in their past four wins, capped with his performance in the qualifying final against the Giants.

The Power kept him to 17 touches and a goal back in round 21, but that win over the Swans was a smashing around the ground.

You don't have to stop him to be successful, however. The Bulldogs beat Sydney at the SCG in round 20, despite Heeney racking up 32 disposals (12 contested), four clearances and a goal assist.

That day the Bulldogs' fierce pressure was too much for the Swans, as they won the contested possession count by 27 and marks inside 50 12-7, with Jamarra Ugle-Hagan kicking four.

The three times that Heeney has had 20 disposals or less in 2024, the Swans have lost.

But Port Adelaide can't afford to put all their effort into one player — because the likes of Errol Gulden, Chad Warner and Tom Papley can also cause havoc if left to their own devices.  

Who wins the aerial battle?

Mitch Georgiades kicked four the last time Port Adelaide played Sydney, and with Todd Marshall out with a concussion and Charlie Dixon a week-to-week proposition right now, the Power will need a similar return from the key forward.

Port Adelaide made the most of their chances, with a whopping 22 marks inside 50 to just four for Sydney. They turned that into a return of 15.6 (96).

If that stat is anything similar at the SCG, then it will likely be a match-winning advantage to the visitors.  

At the other end, the Power took 48 defensive marks between Dan Houston (12), Miles Bergman, Brandon Zerk-Thatcher, Lachie Jones, Logan Evans and Aliir Aliir. With Houston finished for the year, that raises the pressure on the rest of the back six.

But Sydney’s tall forwards have been one of the team’s weaknesses all season. If Sydney is to win, Hayden McLean, Logan McDonald and Joel Amartey need to crash in all night, stop the intercept marks and force the ball to ground.

Slow starting Sydney can’t allow a repeat

It's not exactly a newsflash to say that the Swans have a problem with slow starts.

Infamously, the Swans were 7.3 (45) to 0.0 (0) down after a quarter in round 21 against the Power.

Overall, in 24 games this season, Sydney has averaged 18.6 points for first quarters, with just two goals a game.

Their opponents have averaged 24 points a quarter, including three goals a game.

In 12 games at the SCG, the Swans have won just five first quarters — and that includes the first three home games of the season. So, just two first quarter wins at home after round five, with the last one a 7.4 to 6.3 shootout against Adelaide in the final round.

They have won all five games when they led at home after a quarter. In contrast, the Power has won 17 first quarters out of 25.

They are even better away from home — the Power have won nine first quarters out of 10 away games in 2024.

So it's fair to say that the Swans absolutely cannot afford to snooze through the first half-hour at the SCG.

Geelong vs Brisbane

Familiar foes — familiar result?

Geelong coach Chris Scott has done an amazing job at the club, with his team missing finals just twice in 14 seasons at the helm.

So there is a tendency to see the Cats as the kings of September. However, overall, the team is 14 wins, 15 losses in finals since he took over. That includes a 2-5 record in prelim finals.

On the plus side, however, this will be the third time in five years that Geelong meets Brisbane in a prelim. The previous two occasions? Two wins to the Cats, by an average margin of 55 points.

Does that mean anything for this game? Not necessarily, but combined with the game being played at the MCG — where the Lions have won only three games out of 26 dating back to 2009 — you'd probably prefer to be in the Cats' place.      

Midfield battle may need reinforcements for Cats

Including their crushing qualifying final win over Port Adelaide, the Cats have averaged a tick under 96 points a game in attack in 2024, so they have had no trouble scoring.

That suggests their midfield — and thus supply — must be going all right.

However, part of the success of Geelong this year has been the midfield being bolstered by the likes of forwards Gryan Miers, Brad Close and Shaun Mannagh tracking back to help out and then bursting forward at speed.

Against the Power in week one of finals, it worked a treat, with Geelong winning clearances and contested possessions, and hitting back to earn a massive 22 marks inside 50 to set up a big winning score.

Over the season as a whole, however, Brisbane Lions are number one for clearances, and number one in particular for stoppage clearances.

With Lachie Neale (who may be slowed by a foot injury), Hugh McCluggage, Will Ashcroft and Josh Dunkley all capable of busting things open, the midfield battle will be a key — and the Lions might just fancy their chances.

It also has to be remembered that if you ignore their kicking for goal (see below), the Lions are quite handy in attack themselves, scoring an average of 93.4 points a game.    

Kicking boots essential for Lions

Brisbane will go into the game with confidence off the back of a stunning turnaround against the Giants in Sydney, where the Lions kicked five goals without reply and later seven goals on the spin to overwhelm GWS.

But there is a wider issue at play than the need not to let Jeremy Cameron go crazy in the forward line or let the Cats get 44 (or even 24) points up on them at the MCG.

Put simply, the Lions must bring their kicking boots with them to Melbourne. They must take their chances against Chris Scott's men, and that has been an issue — to say the least — all season for the Queenslanders.

Brisbane has the worst goal conversion of the final four sides in contention for the flag. And it isn't even close.

Over the season, the Lions have scored 333 goals, 336 behinds, or a 49.8 per cent accuracy rate (not counting occasional out-on-the-fulls). The Cats, however, are the best of the remaining teams, with 341 goals 256 behinds, or 57 per cent.

Making Cats pay for turnovers

Geelong may be top of the pops for intercepts, through Tom Stewart, Zach Guthrie, Jack Henry, Mark Blicavs and others.

Stopping Stewart and his influence in particular will be high on Brisbane's priority list.

But the Lions are the best team in the AFL for differential in scoring from turnovers.

Brisbane also turn it over an average of 62.4 times a game, compared to 66.9 for the Cats.

If the Lions can minimise their own errors, hunt Geelong, force the turnovers and make them count, then they will be on the road to victory.