The Brisbane Broncos might be through to their first grand final since 2015 as they look to break a premiership drought breaking back to 2006, but they will need to improve significantly on Saturday night's preliminary final performance to challenge the Penrith Panthers next weekend.

That is going to seem like a strange statement on the surface given they ran up 40 points against the New Zealand Warriors at a packed out Suncorp Stadium.

But it's also the truth.

The scoreboard might have read 42-12 at the end of 80 minutes against the Warriors, but the Broncos were anything but perfect for large portions of the game.

The Warriors simply couldn't make them pay or defend at the same level they have for much of the year to progress to the preliminary final, but if the Panthers are playing at even 75 per cent of their potential, then they will.

And while the Broncos have played better than they did on Saturday evening, the Panthers have an almost scary ability to bring the worst out in their opposition.

There is a reason they have had the NRL's best defence yet again this season, and it isn't even close.

At the end of the regular season, Penrith had conceded just 312 points at just 13 points per game. The next best defence was the Broncos, but they conceded 425 points.

Penrith have then gone on to concede just two tries in their two finals matches.

In Friday night's preliminary final, Penrith let in just a single try against the Storm. Craig Bellamy coached sides in September are usually, at the very least, competitive.

But they simply couldn't find a way to go with Ivan Cleary's Panthers, who aimed up from start to finish and have an extra day's rest heading into the grand final.

Brisbane, on the other hand, let the Warriors score on their first attacking raid, gave away an intercept shortly afterwards and let in three first-half tries during a game which was free-flowing early.

You have to wonder if the Warriors converted all three of their goals as Adam Reynolds did to all four of Brisbane's, whether the game would have taken a different complexion. 24-12 against 24-18 is a very, very different feeling.

Ultimately, we will never know the answer to that, but if Brisbane can't improve on their defence and errors, Penrith will make them pay far more than the Warriors did.

The Broncos wound up making ten errors during the course of the contest against the Warriors, but the period leading up to halftime after they had run up their four first-half tries was particularly alarming.

Both teams dragged each other down the levels, but the Broncos couldn't wrestle the momentum or pull themselves out of the slump.

Despite the 24-12 lead, cameras in the dressing rooms at halftime saw Kevin Walters blasting his team, and he had every reason to given the level of play in the lead-up to the break.

Brisbane put together a far better second half and importantly, their defence appeared to be a focus, but the bottom line remains that if you give Penrith opportunities, they will make you pay.

Again, that's not to say the Broncos can't play better than they did on Saturday, and their 26-0 beatdown of the Storm in the opening week of the finals proves it.

But the Panthers have been at the top of the tree for the best part of four years for a reason, and it's arguable that Nathan Cleary has had his career's best two games in the opening weeks of the finals.

Cleary has pulled apart both the Warriors and Storm in this finals series on the back of James Fisher-Harris, Moses Leota, Isaah Yeo and a bench rotation led by Spencer Leniu dominating.

2022 NRL Grand Final - Panthers v Eels

Brisbane's forwards have been their strong point all season, and Patrick Carrigan on Saturday evening was fantastic in particular, but with an even duel in the forwards, Brisbane giving up opportunities both defensively and with poor ball control will cost them.

The overall consensus seems to be that this will be a close, hard-fought grand final, and there is no reason to believe it won't be, but it'll need Brisbane to be at its best.

If they play like they did on Saturday, they will be beaten soundly, because the only team who have beaten Penrith for much of this season is themselves.

The Broncos are the one side who can match the men from the foot of the mountains, but they need perfection.