Brett McKay dissects key plays that will have a major bearing on the Super Rugby title © Scrum.com

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There's been a surprising amount of discussion as to whether New South Wales Waratahs or the Crusaders start as favourites for the Super Rugby final on Saturday; less surprising is the careful acknowledgement on both sides of the argument of the way both sides can produce points from opposition mistakes. That ability to score from mistakes was never so clear than in the semi-finals last weekend, when both sides capitalised in the most emphatic fashion. So among other obvious dangers, here's something both sides will need to be wary of from the other.

Crusaders: the link men

I've written in Scrum5 columns and spoken in the weekly podcast of the importance to the Crusaders of Kieran Read's and Richie McCaw's link game when attacking from turnover ball, and the Crusaders' first try against the Sharks featured both these players - plus their heir apparent, Matt Todd. It's worth mentioning at this point that four of the Crusaders' five tries came from Sharks mistakes; you'd like to think the Waratahs won't be quite so generous on Saturday night in Sydney, and that previous statement should be motivation enough.

In the opening quarter of the first semi-final in Christchurch, the Sharks displayed the first signs they were playing like no other game they'd played this year - and not in a good way. It was intriguing, for sure, to see the Sharks running the ball out of their own 22, but they also starting coughing up loose ball in attacking territory for the home side.

The Crusaders' first try came from one such soft turnover. Sharks centre Paul Jordaan kicked poorly from just outside his 22, ball only going as far as the halfway line; McCaw fielded the kick under no pressure and passed to a rampaging Nemani Nadolo coming down the near side. Read, McCaw, Todd, and Sam Whitelock followed Nadolo into a ruck down the left, and the Crusaders went wide to the right from there. With no real shape about their attack, the Crusaders came back left from the next ruck, with lock Dominic Bird taking the ball to ground to the right of the posts.

When Andy Ellis looked up from the ruck to the left, his only options in that direction were Todd, McCaw, Read, and Nadolo out on the wing. All four were covered, and the Sharks, in fact, had the numerical advantage.

The Sharks had the numerical advantage before poor decisions in defence © Sky Sports / Fox Sports (Image Supplied)

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The image above shows it all unfolding. After Todd passed to McCaw, Sharks skipper Bismarck du Plessis raced up on the All Blacks captain, who saw him coming and was able to get a quick offload away to Read on his outside. But while du Plessis rushed up, Jordaan hung back, as did JP Pietersen outside him, marking up on Nadolo. The effect of this staggered defence, and du Plessis moving in on McCaw, was to nullify the Sharks' numbers advantage and it Read and Nadolo a one-on-one shot at their opposites.

We know how it played out.

Read is one of the best link-play forwards in world rugby - probably the best, even - and he relishes this roving role down the left side; Jordaan had already allowed him to take the outside running, and the South African's poor attempted tackle put him into space enough to evade easily the covering locks, Stephen Lewies and Willem Alberts. Pietersen staying wide on Nadolo also played a role, but it was just too easy for Read.

The Waratahs can't make this same mistake when Read patrols the left side; they'll need to keep their defensive shape at all times.

Death, taxes, and Kieran Read down the left from broken play... #CRUvSHA

— Brett McKay (@BMcSport) July 26, 2014

Waratahs: the defensive pressure

So much about the Waratahs' impressive win over the Brumbies in the second semi-final was produced on the back of their relentless defence in the second half. As we reported in Scrum5 on Monday, the Brumbies had 15 entries into the Waratahs' 22 for the match yet came away with points only twice, and not at all after half-time.

A lot of that came down to the Waratahs' shape in the defence, and most certainly their communication. I can't recall a NSW player being caught out of position, and their tackle-effectiveness was well above 90% for the match.

Good defensive shape and communication meant that players could make smart decisions, often resulting in Waratahs players shooting out of the line - and that often resulted in a forced Brumbies error. The Tahs first try of the game resulted from one such error.

The Brumbies were on the pick-and-drive early in the game, their first of many forays into the Waratahs' half for the night. They weren't necessarily making a lot of ground, but were making ground nonetheless.

Nic White was seduced by the possibility for an overlap ... © Sky Sports / Fox Sports (Image Supplied)

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Brumbies scrum-half Nic White had prop Ben Alexander coming around the corner, which is the Brumbies' default option in this situation; they've used it for years. But when White looked further out, he was possibly seduced by the apparent overlap at his disposal. Waratahs prop Sekope Kepu was covering Alexander, meaning the Brumbies had four-on-three beyond him. Had Jesse Mogg or Robbie Coleman been able to get the ball in space, they would've been a decent chance of beating the cover defence.

But the Brumbies needed to put the ball through the hands to take advantage of the overlap. Tatafu Polota-Nau knew this, and he got right up in the face of Sam Carter and in fact brought him to ground (which I suppose technically should've been a penalty considering he didn't get the ball).

The point there is that no-one did.

The ball needed to go through the hands to create the overlap, but White instead tried to cut Carter and Tevita Kuridrani out; his pass was too far in front of everyone - and the aforementioned Polota-Nau tackle took Carter and Kuridrani's eyes off the ball.

Alofa Alofa had come up to pressure Jesse Mogg © Sky Sports / Fox Sports (Image Supplied)

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Instead, the ball bounced perfectly for Alofa Alofa, and the Waratahs winger ran 60 metres to score the opening try of the game.

Two things to look at: Alofa can be seen pointing to Kuridrani in the first, and that is exactly the defensive communication the Waratahs used all night; secondly, look how far forward Alofa came to swoop on the ball, relative to how many metres Mogg had moved.

That's defensive pressure.