From playing in the Chiefs Development squad at the start of the season to being included on the blindside of the All Blacks scrum for a crucial Test, it is one of the rarer bolts from the blue in recent New Zealand rugby history.
Sititi said he was excited about being called into action.
"It's a big Test, my first start as well, so I'm excited to see how I do and how I challenge myself."
Part of that will be adjusting to playing on the blindside of the scrum instead of the No8 position where he made his mark with the Chiefs in Super Rugby Pacific earlier in the year.
"I have played a couple of games for [North] Harbour there, that was my most recent experience.
"I'm still feeling a bit overwhelmed but I'm excited and keen to get into it."
He feels his contribution to the team's effort is being able to play for the full 80 minutes and keep a high level of performance throughout.
He's been getting help from the injured Ethan Blackadder, especially in meeting the challenge from Springbok hard man Pieter-Steph du Toit.
"He's very helpful for me in this entire campaign."
Second five-eighths Jordie Barrett said they have prepared well this week, as they did last week, but disappointment lingered from their first Test loss.
Barrett said the changes made to the team were consistent with those in a post-World Cup year.
"We've been through one of them before, and we're not making any excuses in that space. We had plenty of time to prepare.
"This week has been very good as well, but we're facing a very good opposition.
"So, we need to learn fast, adapt, and hopefully do everything we can to get a win."
Barrett isn't expecting too much different from the Springboks from what they have shown over the last six to eight years.
"They've been ultra-consistent. Their form doesn't waver from week to week, and sometimes their selection does.
"They've got a lot of depth."
Bok coach Rassie Erasmus often makes several changes to the side, and he names sides he expects to do the job, which would require a big effort from the All Blacks.
With brother Beauden coming off the bench, he didn't expect too many changes in how he played, apart from wanting to make a difference when he plays.
Barrett said the key for the All Blacks was to keep applying pressure in the moments that matter and not letting the opposition off the hook.
"A little bit of that has been us, and we've tried to focus on those areas throughout the past few weeks. I feel like we're getting there; we're learning. So, hopefully, we see some improvement at the weekend.
Barrett said he had a lot of respect for du Toit, a player who had kept him in check in recent games and who played in three positions last week.
"He's an exceptional player. And he's so versatile, so durable, and covers a lot of the ground. It's inevitable if I'm playing at 12 [second five-eighths], we're going to be running into that channel, and Peter-Steph will be there.
"I enjoy it, it's a great challenge and you want to test yourself against the best."
He said the choice to start Cortez Ratima at halfback and Will Jordan at fullback meant a lot of energy could be expected.
"Tests are difficult, particularly in South Africa. Hopefully, they can go out there and do their basics well. They've got a lot of backing from other players and the coaches.
"It's a great challenge for them and we'll see how they feel."