Let's deal with the elephant in the room first up.
The fact that Australia were forced to play with 14 for 75 minutes against France in the third Test should have never, ever, been the case. In Marika Koroibete's high tackle on France captain Anthony Jelonch from a 4th minute restart, there was clear mitigation to downgrade the Wallabies winger's tackle from a red to a yellow card due to the clear drop in the No. 8's bodyheight moments before impact.
And the less said about Jelonch's Gerard Depardieu performance the better.
But Australia's response to the incident is exactly what this team needed, and a performance that must become a launching pad for even bigger and better things in the future.
"Certainly massive for us," Rennie said after his side had achieved an inspiring 33-30 win in the third Test in Brisbane, in what may prove to be the defining match of his tenure to date. "[We showed] a huge amount of character to lose Filipo [Daugunu] in the first phase and then Marika a handful of minutes later...to play 75 with one man down, amazing character and we're incredibly proud of the boys, I think it will be huge for this group."
The Wallabies' three-point triumph at Suncorp Stadium will live long in the memory for everyone who was there to witness what was a ninth-straight triumph at the venue, so too the thousands watching on at home on television, many of whom will have been in lockdown across greater Sydney and perhaps even down south in Victoria.
That Australia were able to not only manage the loss of Koroibete but also produce their most complete performance of the series is a sign that what Rennie is trying to construct might finally coming to fruition; at last the Wallabies coach saw his team respond to direction and stick to their structures when everything could have completely fallen to pieces.
When fullback Tom Banks dropped the opening high ball in the first minute of Saturday night's encounter, and then winger Filipo Daugunu had to be replaced due to a broken wrist all inside 90 seconds, it was just about the worst possible start for the Wallabies.
At least until Koroibete, Jelonch and the refereeing team, led by New Zealander Ben O'Keeffe, all sprung into action.
The French immediately capitalised on Koroibete's dismissal through scrum-half Baptiste Couilloud, though the No. 9's leading arm as he ran straight over the top of Tate McDermott drew more than just a few curious boos from the parochial local crowd.
McDermott could have let that moment spoil his match. But the Wallabies halfback, who was called up in place of Jake Gordon, went on to have a superb first run-on start.
The difference in the Wallabies' attack compared with the first two Tests was stark early on in Brisbane, as a beautifully-flat Noah Lolesio pass found a rampaging Michael Hooper, the skipper charging through the French defence and then finding the supporting McDermott for a try that suggested Australia could truly do something special.
From there, it was another gripping tit-for-tat encounter of Test rugby that has been the central theme of this exceptional series.
The boot of Melvyn Jaminet was again ever present in Brisbane, so too Wallabies fly-half Lolesio, no more so than in the game's closing stages.
But before that there was an intercept try from Lolesio; the craft of Cameron Woki, who reached out with his seemingly never-ending arm to land a vital blow before the break; the brilliant play of Couilloud and winger Teddy Thomas that put Pierre Louis-Barassi over; the power of the Wallabies scrum and replacement prop Taniela Tupou; vital covering defence and turnovers from Isi Naisarani and further drama with another TMO intervention and a correct overruling of a Wallabies try.
This Test really did have it all.
In the end it came down to the kicking nerve of Lolesio and Jaminet, and one final decision from French skipper Jelonch, after the visitors' final penalty was deemed to be beyond Jaminet's reach.
The French kicked to the line and attempted to set up the rolling maul from 25 metres out, but were disrupted by Wallabies rookie Darcy Swain. O'Keeffe's final whistle sent the local crowd delirious.
The Wallabies have a good one in Swain. Having come off the bench late in the first two games, Swain turned in an 80-minute performance that proved he is very much a Test player. The Brumbies lock hit rucks, carried with purpose and defended stoutly, and did the nuts and bolts of his role by winning his lineout ball.
"I thought he had a massive impact today, not just in moments late in the game but throughout," Rennie said of Swain. "We were able to put their set-piece under pressure, and Darcy was a big part of that and it's the reason we picked him.
"So he's found his feet quickly and deserved his start, and had a big say in the game today."
Replacing Harry Wilson at No. 8, this was also Naisarani's best game in the Wallabies jersey. He may be heading offshore at the end of this international season, but it is clear the message Rennie sent the Fijian-born back-rower last year, with a reminder this season, has been well and truly received.
The duo was ably supported by Brendan Paenga-Amosa and Lachie Swinton. The Wallabies' entire pack, in fact, clearly upped their game from Melbourne with the attacking ruck a huge improvement and the exchange of passing in tight much better organised.
Australia's attack was, on the whole, a different proposition to that which had fronted in both Brisbane and Melbourne earlier in the series. While there were still moments of the "out-the-back" play that had been so easily stifled by France's rush defence, Australia were more prepared to go through the middle of the paddock and play at the defensive line.
The Wallabies' also at last employed a "smart kicking game", which Rennie had referenced in the build-up to the decider. Having hardly gone to the boot at all in Melbourne, McDermott's box-kicking was on target and well supported on the chase by Reece Hodge.
Lolesio, too, delivered the kick pressure that forced French replacement Alexandre Becognee into the knock-on that gave the Wallabies the chance to continue their dominance at scrum time. They did just that, and then Lolesio -- having already gathered himself from a simple missed penalty midway through the second half -- held his nerve to again answer Jaminet and deliver the match-winner.
"We put a lot of young men on the park tonight, didn't we? And they repaid us in spades," Rennie said of his new Wallabies brigade.
"We're creating good depth, we're creating competition for places and I just think this is massive for us because it just gives you belief; it just highlighted how tight they are as a group, how hard they've worked with each other and for each other. It's a helluva effort."
But this wasn't the perfect performance from the Wallabies either and they will be in no confusion about the challenge that awaits against the All Blacks in three weeks' time. At Eden Park, to boot.
Australia's inability to shut the game down following Lolesio's 78th minute penalty is an example of one key work-on moving forward.
Looking ahead, Rennie should welcome back a few more troops for the Bledisloe Cup and Rugby Championship campaign and he faces a potentially difficult decision in the halves with Nic White and James O'Connor sure to come into contention if they are indeed fit.
Just what becomes of Koroibete over the next few days will be keenly watched, not just in Australia but around the globe. The absence of both the yellow and red cards had been a pleasing sidenote to this series before Saturday night, but in a few minutes was quickly ripped to shreds and rugby stakeholders of all types will be scratching their heads and debating the ongoing issue of consistency.
Coincidentally, South Africa Director of Rugby and World Cup winning Springboks coach Rassie Erasmus had only 24 hours earlier taken to social media to raise an issue with British & Irish Lions centre Owen Farrell's tackling technique ahead of the first Test next week. Make of that what you will.
The uncertainty and inconsistency around foul play in rugby is in no way a new issue, but it retains a place firmly among the game's key problem areas. The fact that World Rugby was unable to push through its red-card replacement trial, which was employed successfully in both Australia and New Zealand's domestic competitions, also serves to irk the ire of supporters, those with borders on the Tasman Sea in particular.
Those who support the Wallabies will, for now, savour this famous win and hope that it really is the start of something special.
Regardless of their memorable triumph and long overdue series victory -- Australia had lost each of their most recent mid-year three-Test series against England and Ireland -- the Wallabies will head to Eden Park with little to no expectation that they might end up on the right side of the ledger in Auckland for the first time since 1986.
Then again, no one truly expected them to be able to play a man down for 75 minutes and win at Suncorp Stadium either. Self-belief is a powerful thing.
For the first time in a while, the Wallabies should have it by the bucket-load.