It's seven years since Johnny Sexton last started on the Irish bench.

For almost seven years now, if Johnny Sexton plays he starts.

When Sexton last started a game sitting on an Irish subs bench, it was at the expense of Ronan O'Gara at the 'Cake Tin' in Wellington, in that World Cup quarter final defeat to Wales in 2011, almost seven years ago.

Every O'Gara kick was twinned with a camera staring at the bench, gauging the reaction of Sexton. When Sexton played in that tournament, the cameras did the same to ROG.

Joey Carbery has quite a way to go before creating that level of rivalry with Sexton for a number 10 shirt, but his selection for the opening test in Brisbane is a statement of-sorts by Joe Schmidt.

Carbery has played at outhalf for Ireland before off the bench. He's started twice in the 10 shirt, once when Sexton was on Lions duty, and once more when he was rested entirely.

In part, it seems like a reward for Carbery taking Schmidt's advice and leaving Leinster for Munster, where he's likely to gain more 'big-game' experience in his favoured position. While Sexton is one of several Leinster double winners rested to the bench, it gives reassurance to the 22-year-old that he's more than a break-glass-in-case-of-emergency option.

It's going to be a huge climb up the learning curve for Carbery this Saturday. Australia at the Suncorp Stadium is far removed from Fiji and the USA, the opposition for his two previous starts at outhalf. He'll be navigating his way through an incredibly experienced backline; Will Genia, Bernard Foley, Tevita Kuridrani, Israel Folau, Kurtley Beale will no doubt be putting a target on his back.

Luckily, the game won't make or break his chances of playing again. The pressure put on him to move to Munster shows how much emphasis the IRFU are placing on his development. This is just another step, a test of his ability to control a game against top quality test opposition.

His relationship with future provincial teammate Conor Murray will also be worth watching. In his 10 caps to date, he's played less that 40 minutes in total as as Murray's half back partner. Much of Ireland's success in attack comes from the familiarity between Murray and Sexton, and their ability to know what the other will do in a split-second. It was a relationship that wasn't just born, but developed. Every minute they play together between now and the 2019 World Cup will be invaluable.

The added benefit is that Murray's experience is perfect for Carbery's growth. In much of Carbery's appearances for both club and country, he's been paired with scrum halves of similar experience levels. Murray's dominant persona and standing in the game can be the security blanket, allowing Carbery the confidence to play his game.