Of all the halfback combinations at this World Cup, my view is that Conor Murray and Johnny Sexton are the best. By that I mean that they can get their team clicking better than any other combination. They are the ones to aspire to. You can't say that of New Zealand's Aaron Smith and Beauden Barrett any more because Barrett is now at full back. So, purely on getting the most from the sum of their parts, Murray and Sexton are the best.
There is some quite tasty recent history between Ireland and the All Blacks but, as a Kiwi, I still don't regard Ireland as our bogey team. If anything, that is still the French, even though they haven't tipped us up in a World Cup since 2007.
Yet New Zealanders do consider Ireland to be a really, really good team - a team they respect and a team for whom they have to be at their best - and that is accentuated when Murray and Sexton are playing together.
The reason I worry is because what they achieve as a pair and what they get out of guys around them is vastly more than they manage as individuals.
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Players around them get comfortable having the two voices there that they know and trust and their confidence grows because they are not having to worry about things because it is being seen for them.
I know that there has been concern for a while about Sexton's form and fitness, but I dismiss that. I expect him to be on form against New Zealand today. I am sure that Ireland have been managing his work rate. For the past two years, they'll have been working him to this moment.
Murray and Sexton have played only twice together in this World Cup. They were convincing against Scotland and weren't playing together when Ireland lost to Japan.
As a pair, what makes them so effective is how their partnership adds value to each of their games. Individually, they are both good enough to dictate the course of a match. Like everyone, the All Blacks will be putting a lot of pressure on Sexton, but that's when Murray puts his hand up and takes it on. They can mix and match like that. That is the main concern for me; I'd be far less worried if one of them wasn't playing.
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In a halfback pairing, it helps if you like to play the same type of game but sometimes it actually works to have guys who are different and complement one another - like Murray and Sexton.
When I played with Justin Marshall we were a bit like that. He was quite a different player to me, a more physical and combative player looking for a direct approach and I was more looking for space. He would see things that I didn't and vice versa. The important thing is being decisive. If there is a good channel of communication, then, right or wrong, you go with one.
That's not just a 9-10 thing. Look at Ma'a Nonu and Conrad Smith at centre: seeing completely different things, operating as different individuals but working well together. Again, the key is communication.
With Murray and Sexton, I see Sexton as more like me. He is more physical than I was but still tends to be looking for space. Murray is a guy who is looking at that combat. His attitude is: let's punch.
When I look elsewhere around the quarter-finals, I see Australia and I really don't know what the plan is. I know Michael Cheika and I like him as a coach and he may have a grand plan, but I can't see it. You want your halfback pairing to settle. I think you want to show some sort of pattern.
Australia could prove us all wrong by having a game plan up their sleeve but if there were one, I think we would have seen it more against Wales in the pool stage. I thought that was an interesting game - to be suddenly chucking in Bernard Foley at No 10, when he hadn't played much and had probably had his confidence knocked, didn't seem right.
Frankly, the way they have gone, I can't see them getting near England. I can't see them winning enough ball or, against the English defence, being able to effectively use what ball they do get. I just don't think that they have the capacity to score points.
Australia should look at Ireland and how long they have had their No 9 and No 10 together. Now that is a way to forge a partnership.
(Andrew Mehrtens won 70 caps for New Zealand at fly half between 1995 and 2004)
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