"ROTATION of players affects the fluency of how you play... you can kind of rotate the front half of your team and still sort of have some stability and consistency in results but if you have to change centre-backs and defenders regularly, you're going to struggle."

Ange Postecoglou, who said those words, has certainly not had his struggles to seek since joining Celtic in June. The defence has, arguably, been his main headache.

Between a frustratingly slow pace of recruitment, injuries to key players and boardroom unrest, the 56-year-old has quickly learned there is never a dull day at the helm of a truly big club.

One of the top priorities in the Greek-Australian's in-tray when he took the reins was a centre-back. At least one of them.

It did not happen right away. With Christopher Jullien injured and Kristoffer Ajer departing for Brentford, Postecoglou was left with no option but to start Nir Bitton - a defensive midfielder by trade - at the heart of defence alongside the relatively inexperienced Stephen Welsh for the Champions League qualifying first leg against FC Midtjylland.

That Bitton got himself sent off in spectacularly senseless fashion during that game meant that, by the time the return leg rolled around, it was the even less experienced Dane Murray taking his place to partner Welsh.

The club then purchased Sweden international Carl Starfelt from Russian side Rubin Kazan to help keep the back door shut and allow the forward players to run riot through the rest of the house in Postecoglou's high-intensity attacking system.

Bitton came back in to partner the new guy for a couple of games - a league-opening defeat to Hearts and Tynecastle and a 4-2 away win at FK Jablonec in Europa League qualifying - before the Hoops embarked on a seven-match run with a Welsh-Starfelt defensive axis.

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Of those seven matches - which represent half of Postecoglou's competitive tenure so far - Celtic won five and lost two while keeping four clean sheets.

Other context matters too, though. After the Hearts defeat Celtic enjoyed five home matches in a row. Given Postecoglou's pass-and-move style, playing on that big Parkhead pitch can justifiably be said to suit the Hoops better. 

Midway through that run, he made the decision to switch Welsh from right centre-back to left and Starfelt vice-versa. Whether this was done simply to make Starfelt, hitherto somewhat struggling to adapt to life at Celtic, more comfortable (he played right at Goteborg and with Kazan at first) or with an eye on his ultimate partnership encompassing a fit-again Christopher Jullien is unknowable as yet.

Regardless, the two were swapped back again for the trip to Ibrox at the end of August - a match in which Celtic's set-piece defending was once again placed under the spotlight - and the partnership has not been sighted since.

Celtic Way:

Part of the reason is that transfer deadline day heralded the arrival of another centre-back, this time United States of America international Cameron Carter-Vickers on loan from Tottenham.

Since his arrival Carter-Vickers has started three games, winning the first against Ross County and losing the next two against Real Betis and Livingston. The American, playing on the right of the central pairing, partnered fellow new recruit Starfelt before Welsh was drafted in for the Livi game.

In case you haven't been keeping count, that's a grand total of six different central-defensive partnerships in Postecoglou's first 14 games.

If we take into consideration that the Welsh-Starfelt pairing has included both players switching between right and left centre-back on a couple of occasions then that lack of consistency is extended yet further.

But Postecoglou would rather it wasn't like this. We know that because he's told us before - lets consider that quote from the beginning of the article again...

Rotation of players affects the fluency of how you play... you can kind of rotate the front half of your team and still sort of have some stability and consistency in results but if you have to change centre-backs and defenders regularly, you're going to struggle."

So when asked his thoughts on the concept of rotation and areas that should be almost immune from it, the manager was unequivocal: central defence should pretty much be a constant, one of the few fundamental reliability factors in a system geared towards relentless attack and explosive scorelines.

A quick look at Postecoglou's past successes demonstrates that his belief in that sentiment is not just him paying lip service or posturing. He has lived it before.

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While his triumphs have owed much to his attacking philosophy, his latest truly great teams were built on the back of consistent centre-back pairings.

Yokohama F Marinos' 2019 title-winning team had at its core centre-backs Thiago Martins and Shinnosuke Hatanaka; the two started 33 out of 34 league games together as Postecoglou led the club to its first J1 League title for 15 years.

Likewise, his historic Brisbane Roar side had as its bonafide mainstays Matt Smith (all 30 league matches) and Milan Susak (26 of 30). While he was in charge in Brisbane, Postecoglou oversaw an Australian-record 36-game unbeaten streak with Smith playing every game of the Roar's historic run while Susak played in 25 of the first 28 of those before departing the club. 

Once more it's worth keeping in mind Postecoglou's own words on the importance of having central-defensive mainstays at his disposal. If you have to change centre-backs regularly, you're going to struggle.

He was speaking during his time in Japan, of course, but the sentiment rings as true in Glasgow as it did in Yokohama or Brisbane. The sooner Postecoglou can nail down his preferred centre-back pairing, the better it will be for Celtic.