‘Welcome to Celtic’ said Ange Postecoglou, where there are no soft introductions, nor excuses for losing 3-0 to Rangers.

It was tricky to decipher whether the Parkhead manager regretted making six changes to the side which clinched the Premiership title in Edinburgh last week, or handing first derby starts to three players in Yuki Kobayashi, Oh Hyeoun-gyu and Alexandro Bernabei.

The scoreboard at full-time would suggest so, yet this was a day where Postecoglou may just have learned a valuable thing or two about individuals who have been on the fringes of his squad. It is not often a Celtic manager finds himself in a position to experiment at Ibrox without the threat of tangible consequences should it backfire. Defeat here was frustrating for him, of course, but must be viewed within the context of the season.

With the league trophy already booked in for a presentation at Celtic Park later this month, he basically confirmed at his Friday press conference that this match would be an opportunity for some of the relative newcomers to the, shall we say, eccentricities of this fixture to immerse themselves in it.

These two clubs remain miles apart on the continually thorny issue of away allocations, so these days there are no more hostile arenas than this for anyone wearing a green and white jersey. Given how disappointingly the season has panned out for Rangers, Ibrox was not exactly rocking pre-kick-off.

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But the 50,000 or so who turned out reacted to their team’s intensity from the very off, building a wall of noise that did seem to leave Celtic in an early tailspin. Those are the moments Postecoglou will have looked closely at his derby rookies, to assess their resilience in the face of adversity.

On this day, at least, he will not have been hugely encouraged.

It’s no secret these games are as much a test of character as they are footballing ability, and the early storm was, in some ways, the ideal test for those who had not stepped into the breach before. What Rangers have found to their cost this season is that failure to capitalise on the big moments is so often the losing team’s undoing. Oh was presented with his mere minutes after Rangers opened the scoring, and he could not make it count.

There is no question over who Celtic’s number one striker is, and Oh will have arrived at Celtic Park fully aware of the fact that ousting Kyogo Furuhashi from the starting line-up would be a tall order. It is hard to imagine Kyogo missing the chance his understudy clipped against the post after being teed-up superbly by Liel Abada.

The South Korean barely had look-in afterwards.

He looked disappointed on his way off the pitch, but it will be a valuable lesson for the 22-year-old – still in the very early stages of his Celtic career – that fluffing your lines on these occasions is not an option.

It was tougher afternoon for his team-mate Kobayashi. The Japanese centre-back has found himself thrust into two of Scottish football’s most testing environment two weeks on the trot, burdened with the responsibility of emulating the imperious Cameron Carter-Vickers. The American is the ideal defender in these games – he rarely loses a duel and is ultra-calm under pressure.

The same could not be said for Kobayashi on the day. There was a passiveness about his performance, one that played into the hands of a Rangers forward line that was all about aggression. There was nothing particularly nuanced about the proposition Fashion Sakala and Rabbi Matondo presented Celtic’s back four, but their directness and readiness to be absolute nuisances was enough to unsettle them. A more clinical forward pairing may have even more joy on the day. Kobayashi was found wanting for Rangers’ second, finding himself bullied by John Souttar as he powered home an unstoppable header.

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It is hardly an incredible revelation that this team will miss their £6m, Player of the Year nominated centre-back, and when he returns from injury he will play most, if not all, of these games. But what has been so impressive about Celtic over the season has been the seamlessness with which players have stepped into the team when others are missing. For perhaps the first time, that could not be said.

Like Oh, however, Kobayashi’s Celtic career is a fledgling one, and the whole point of days like these were to show him what this fixture demands of you. That being said, you don’t get too many opportunities to acclimatise, and any lessons learned from this must be learned quickly.

Given the incredible growth Greg Taylor has enjoyed this season, it would be folly to make sweeping statements about Celtic left-backs, but Bernabei is currently well short of the levels being reached by his team-mate this season. His use of the ball is erratic and defensively he is unconvincing.

Yes, he too is young, but for the £3m-plus paid to Lanus last summer, you’d expect a little more.

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Other than some players still having much to prove, it is difficult to draw too many conclusions from yesterday, or infer much about what, if anything, it means for next season. Celtic will probably never line up like this against Rangers when there’s something on the line, and several of this Rangers team will not be around to do it all over again next season.

The occasional jolt can be a good thing, though, and even this all-conquering Celtic team can benefit from a timely reminder they cannot ever take their foot off the gas.