You don't do that in your first senior competition seemingly without a care in the world without having something special.
It's an attribute many athletes, including plenty of Kiwis over the years, have struggled with - the ability to cope with the big stage, the big occasion, and own it.
Even on that super Saturday, when she had a nation enthralled on her way to Olympic bronze, a mate said to me, "we've already got the boardroom booked Monday morning to discuss how we unite the McCartney brand with ours".
Join the queue, fellas! Talking to her manager, Scott Newman, he's never seen interest like it. On Thursday, he took Eliza through no less than 30 commercial opportunities.
Imagine the list: probably an airline, car manufacturer, clothing brand and an endless array of food options, and you suddenly have one very successful and financially secure 19-year-old.
Even when it comes to social media, she's in a different stratosphere. When I post anything Eliza on my VeitchyonSport page, it goes nuts. I'm talking Steven Adams proportions here. This teenager has quickly become a rock star of New Zealand sport.
Which leads me to these questions:
Who is New Zealand's most marketable athlete? And who is the athlete you would most want to listen to and get a selfie with?
Here are some options:
Eliza McCartney
Beauden Barrett
Sonny Bill Williams
Steven Adams
Aaron Smith
Lisa Carrington
Peter Burling and Blair Tuke
Do we still include Richie McCaw?
I'm sure there are many more candidates. Vote away people...
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To sack or not to sack
Let me take you back to a conversation I had with Warriors owner Eric Watson in April. It was a broad-ranging interview on how his club can move from NRL underachievers to genuine title contenders.
The line of questioning eventually turned to Andrew McFadden and his hold on the Warriors coaching job if 2016 did not play out as expected. I kept Watson's answer on file, because his response was interesting. Our interaction went like this:
Question: What of the coach? Is he secure beyond 2016?
Watson: (long pause) Yes.
Question: So you're telling me he's safe even if they were to lose their last eight games of the season and miss the eight.
Watson: They won't miss the eight.
That reply was straight and to the point. So here's the Grand Canyon-sized problem for the Warriors. Now they've missed the playoffs again, what happens with McFadden?
I'll put my marker in the sand. I read with interest the options for a replacement being put forward. Forget Craig Bellamy, they've already tried to lure him and he's contracted to the Storm. David Kidwell has put his hand up but he missed out on the job to Cappy in the first place, and he'd be coming from the Tigers, a club with its own share of dramas.
I think there are really only two options. The first is to keep McFadden. The players are saying all the right things, even behind the scenes, which is crucial. There does not seem to be a campaign of leaks revealing a divide between players and coach. But if he is retained, they all need to get their act together in 2017.
The second option is Stephen Kearney, the Kiwis coach who's served under Craig Bellamy and now Wayne Bennett with the Kiwis and Broncos. Yes, he failed to make a fist of it as Parramatta Eels coach, but has that experience in conjunction with his latest time with Bennett taken Kearney to the next coaching level?
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Email of the week
I take my hat off to the diehard Warriors fans who follow the club through defeat, constant failure and underachievement. They are the most loyal in Kiwi sport, summed up by this message from Kurt, obviously one of their hardcore fans.
"Through thick and thin, season after season, we've raised our arms in victory and covered our faces in despair.
"We've shouted, cheered, groaned and applauded alongside all those who have stood, rain, hail and shine, in the grandstands or on the sidelines, at their local or in their living rooms.
"With voices raised in unison, we've watched mesmerised, holding our breath and screaming with joy, not just a game, not just a team, but a battle to the end.
"Every minute, of every half, of every game, season after season. We are your supporters. Warriors together, forever. #Faither Vodafone Warriors