"I was playing hooker out at Pakuranga, but when I got into the prems team, the hooker was the captain - kind of like this team," he chuckled motioning to his Blues colleagues.
McCartney moved into loosehead prop about eight years ago and has repeated those duties with Auckland during the ITM Cup when he shifted out from hooker as substitutions were made late in a game.
He also started a couple of games as prop for the Blues last year but that was an infrequent selection. The roles were very different.
"The main thing you notice at prop is your legs are gone a lot earlier than they would be at hooker," McCartney said. "If you are having a good battle at prop, it can blow your legs out much quicker in a game.
"I don't know if that is me finding my way into the position again but I have noticed that. However, being able to cover a couple of positions for the coaches is valuable for them and me."
It means an increased workload off the park for McCartney as he has to prepare physically for both positions and also be right up to speed with the calls for lineout throws.
The Blues have just two hookers in their squad so if Mealamu is damaged, McCartney has to slot into those duties.
Opening night of this Super 15 was a rugged propping task for McCartney as he squared off against the All Black Franks brothers.
But McCartney reckoned it was magic to work against the best.
"Who else would you want to test yourself against but those guys?" he asked. "By no means did I get pushed off the park although they got a decent hit on us a couple of times.
"If you let them get into a good position and let them extend it out then they are hard to move.
"Owen Franks is a big man and up there with the strongest in Super 15 if not the world. He is the cornerstone of the All Blacks scrum and a very experienced rugby player. It is great to see how you measure up against him."
Tonight's foes are the Chiefs who have been experiencing their own front-row dramas and have picked Ben Tameifuna to make his debut against McCartney.
"We would be foolish to think it is going to be anything but a great battle, attitude is everything," McCartney warned.
"We were patchy last week at setpiece especially at lineout with tap backs and our work there was lethargic and Sam Whitelock and Tom Donnelly dominated. That pressure meant our backs struggled to find any rhythm. We all need to up our game for this one."