Why Celtic's squad is finally being built to last - Sean Martin

In another victory for the collective, arguably the most encouraging part of it was the lack of standout performers; every player in green and white played their part and each, crucially, looked like they were having a wonderful time doing so.

The back four stayed alert, built up from the back and made their presence felt in the St Johnstone half. The midfield overwhelmed the visitors with persistence and panache. The forward line was as fluid as it has been in years.

But there are other takeaways too. Ones that, you feel, extend beyond the game itself.

Ange Postecoglou is building something. Duh. Beautiful houses, creating special things, we don't stop. We know, we know!

It’s true, though. Summer is going to be so important in that regard. It's phase three of the Postecoglou rebuild and should be treated accordingly whether Celtic win a treble or not. There are a few places where the starting XI can still improve for the European stage that the manager craves to make an impact on.

The good thing is that the platform is, mostly, already there. Vitally, the majority of the main contributors this season are at favourable stages of their careers.

READ MORE: Detailed Celtic player ratings as Matt O'Riley and Daizen Maeda take centre stage in ruthless seven-goal showing

The average age of the starting XI against St Johnstone was 26.3. Remove 34-year-old goalkeeper Joe Hart from the equation and the outfield 10 had an average age of just older than 25.

Of course, there are two loanees in there (technically three, if you want to include Daizen Maeda). Cameron Carter-Vickers and Jota, at 24 and 23 respectively, are the top two on most fans' wishlists when it comes to summer recruitment; how those deals play out will no doubt dictate much of the rest of the club’s business.

But the bench, arguably, is where the reasons to get excited really lay on Saturday. Postecoglou opted to use all five of his available substitutions against the Saints. The quintet removed were ‘big’ players but the impact of their replacements allowed us another glimpse of what it looks like when the strength to ensure Plan A can retain its intensity is readily available to call upon.

Giorgos Giakoumakis has picked up a knock? OK, Liel Abada can come on and Maeda will go through the middle. Tom Rogic to go off at half-time? OK, here's Matt O'Riley to torment you for the next 45. Reo Hatate needing a rest? No worries, David Turnbull's champing at the bit here. Jota is untouchable, no? Nah, there's Kyogo Furuhashi to lift the roof off Parkhead. James McCarthy replacing Callum McGregor is the exception that proves the rule.

Moreover, the players who came on carried an average age of 24.2. Take away McCarthy, whose role next season remains murky despite his lengthy contract, and it was just 22.5.

That's the beauty of this squad. Still in its infancy as a group, it is already being built to last. To grow together, to win together, to achieve together.

Beyond the guys who played yesterday James Forrest is still to return – a reduced role in the offing or not, he can still contribute if fit – while look one rung down and Karamoko Dembele's contract situation looms over his future at the club. Whether the likes of Johnny Kenny, Owen Moffat and Joey Dawson are able to step up from B team football to claim what will be a highly-coveted place in the senior squad next term also remains to be seen.

But Postecoglou has made it clear if they, or any other young Celts, show their quality in training they will get a chance as long as they want to be there. It bodes well.

Now, the caveat to these things concerns the broader view of football operations. The term 'modernisation' gets thrown around a lot these days - it was the buzzword around the failings of last season, certainly - but it does have its merits.

Dermot Desmond's interview covered many things but debatably the most illuminating parts were the hints he gave in to some of the behind-the-scenes processes that exist at the club.

The recruitment of Postecoglou in particular - which Desmond seemed to admit rested almost entirely on Peter Lawwell's insistence that Postecoglou appear on the pair's fabled 'five-man list' - must surely bring that term 'modernisation' to the fore again for fans interested in the operational side of matters at Parkhead.

READ MORE: How Celtic ripped St Johnstone asunder in Parkhead pummelling

Where the recruitment of playing staff is concerned, Desmond said: "The manager of the club has always been, in the last 20 odd years, who decides what players to take in. Not the board, not anybody else.

"There are searches to provide information to the manager, the manager then makes the decision, maybe in conjunction with his coaching staff. He makes the ultimate decision. He's chairman of the board. Ange is chairman of the board at Celtic as far as football recruitment is concerned and all things football are concerned.”

The importance of Postecoglou to the way the next few years plays out - and probably beyond that - is hard to understate now. He is on a one-year rolling contract. That's fine, as long as it's fine. But the "manager is the chairman of the board" attitude is only good for the club in the long haul if the structure surrounding him reflects a coherent underlying ethos whether the figurehead is there or not. It shouldn't chop and change with whoever's in the hotseat, but transcend the position even if it's based on an individual's philosophy.

If Postecoglou's role is truly an almost NBA-style hybrid of head coach and general manager then the club must be proactive in ensuring not just that he's at Parkhead for the longer term but that the operation around him is geared towards functioning at a cogent, elite level even if he were to depart for any reason.

The value of having an identity on the pitch is playing out in front of thousands every single week. The same must become true off the pitch too.

With a young squad, a trustworthy manager and a clear vision for on-field success, the tools are there in the months and years ahead for Celtic and Postecoglou to build not only this 'beautiful house' he goes on about but a whole damn skyline.