After a first win on South African soil, the expectation the following week was that more of the same would follow, at least in terms of Ireland's team selection.
But Joe Schmidt surprised many when he opted to make five changes. Having had his squad depth so badly stretched at the World Cup the previous year, the Kiwi had to plan with the long-game in sight.
Plenty of eyebrows were raised when Mike Ross was omitted from the match-day squad entirely. The tighthead's starting place instead went to Tadhg Furlong, who hasn't looked back since.
Fewer than five months after sealing that historic win, Ireland followed it up by doing the same to the All Blacks.
Earlier that year, in 2016, Paul O'Connell was forced to retire, and somewhere far away from the limelight, the legendary lock was smiling to himself.
Ireland's strength in depth has again been tested throughout this season's Six Nations and so far, they have come up with all of the answers.
When O'Connell hung up his boots and Ross soon followed, there were legitimate concerns about the front five, yet that has been an area of strength for Ireland in recent times.
"It is amazing at the moment," O'Connell maintains.
"I think everyone used to talk about the enforcer in rugby in the number four lock. That's gone out of the game really.
"It is just about being technically excellent at the breakdown, at the scrum, at the maul, at maul defence, technically excellent in the defensive line where the front five tend to be; one, two, three, four, five out from the ruck.
"I think that's what we have, technically. Obviously, they are big, very powerful men. But technically, they are excellent.
"The way they defend the maul, when they get a five-metre crack themselves, the way they've managed to get over the line and score.
"The ruck has been brilliant for Ireland as well. I think we have big, powerful men in that position that are technically very good rugby players as well.
"The prop situation is amazing from where we were five years ago. There is a queue of tighthead props. It is amazing.
"All the provinces seem to have a few tightheads now. We were in the situation where there was one prop in the country there for a while.
"It is brilliant. It goes back to that South Africa game after we won that first Test. It's all been about building depth in the squad. For the first time ever, Ireland have serious depth in the squad."
Building depth is currently something O'Connell is trying to do in his role as forwards coach with the Ireland U-20s.
Defeats to France and Wales have derailed their Six Nations hopes, but with a World Cup to come in June, there is still plenty to play for.
The U-20s have had two training sessions with Schmidt's side in recent weeks, and while it is easy to point to the learnings that the young players get from being exposed to the highest level, the same idea applies to the inexperienced coaching group.
The joined-up thinking from the top down is typified by the players hearing Schmidt relay similar messages to his players as O'Connell and Co while at the same time, it also acts as a reminder to the U-20s coaches that they are on the right path themselves.
"We're trying to do a lot of similar things to what the seniors do, so when they hear Joe talking about a lot of the things we're speaking about, doing a lot of the drills we're doing," O'Connell explains.
"I suppose it just compounds the message and they are really high-intensity sessions as well.
"Probably in terms of physicality, there isn't a big difference between these guys and where those seniors were when they were 20, but they've had a lot of coaching and there is so much detail in the game now.
"Players who can take on that coaching and not let it affect their game from a physical point of view are the ones who are thriving and who are most successful at the moment.
"Sometimes for our guys it might seem like a massive jump but it isn't really, you just have to take it kind of day-by-day, bank a bit of knowledge and move on to the next thing.
"The (senior) coaches are brilliant that way to chat to. They're great to spend time with and run things by and I think because we're doing, well we're trying to do a lot of similar things. It probably doesn't look very similar, but they had some of the same problems as we've had.
"In fairness, you can text any one of them (coaches) at any time of the day and they'll always come back to you by that evening. That's really, really enjoyable to have that kind of resource available."
Independent.ie's U-20s Six Nations coverage is in association with PwC