Ange Postecoglou admits defeat at Ibrox was a crash course in life as a Celtic player for the fringe men who failed to impress against Rangers.

The Parkhead side, crowned Premiership champions last week, suffered only their second domestic defeat of the season as they went down 3-0 at the home of their city rivals. Postecoglou made six changes to his line-up, some of them enforced by injury, and handed first derby starts to the likes of Yuki Kobayashi, Alexandro Bernabei and Oh Hyeun-Gyu.

But it was a trio of Rangers players who made the difference, with goals from Todd Cantwell, John Souttar and Fashion Sakala earning Michael Beale his first victory over Celtic as manager. Postecoglou conceded that several alterations to the team which beat Hearts last week was destabilising to an extent, but he stressed there will never be a ‘cushy introduction’ for players who must quickly understand what is expected of them.

“It does [have an impact] when you change things,” the Celtic manager said. “But at the same time it is an opportunity for guys. It is a tough place to get an opportunity, but it is not the first time certainly I’ve done that and sometimes giving guys debuts in these games.

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“They just need to understand what this football club’s about, that’s the expectations. You don’t get an easy ride, you don’t get  a cushy introduction into life as a footballer. It is demanding from the moment you put on a shirt to the moment you leave.

“It is fair to say it wasn’t just about the guys who came in. Obviously the changes didn’t help but I just thought the general performance, and the level of performance, wasn’t there.”

What disappointed Postecoglou most is that he felt Celtic ‘accepted their fate’ as Rangers added to their lead. They found themselves 2-0 down at half-time and never really threatened to mount a comeback following the restart. Their best chance fell to Oh moments after Cantwell opened the scoring, but the striker’s dink hit the post as he went one-on-one with keeper Robby McCrorie.

‘It is a big moment,” Postecoglou said. “They were up for it, the crowd were up for it and they get a goal. If we could hit back straight away, it takes a bit of the momentum out of them.

“The big man probably should have put it away. He hits the post, so it wasn’t far off. I think it is a bit of a learning experience for him as well. When he looks at someone like Kyogo, he misses goals too, but it doesn’t affect him afterwards.

“He is still running his socks off for the team. In the second half, I just felt we almost accepted our fate rather than sort of going out there to try and change the course of the game.”

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Despite his frustration, Postecoglou emphasised Celtic’s outstanding season has not been diminished, and they are heavy favourites to complete the treble by beating Inverness Caledonian Thistle in next month’s Scottish Cup final.

Being confirmed as champions last week was the culmination of going unbeaten in the league since September, and the title race was all-but over months before the maths rubber-stamped a second successive championship. Postecoglou believes it was ‘weird’ that Celtic had another away game after getting over the line last week, but that it is simply another example of the demands his players must deal with week-to-week.

“They are human beings and they have had an outstanding season,” said Postecoglou. “We had the euphoria of winning the title last week and it is kind of weird winning it and you are having to play away again. You don’t really get a chance to sort of appreciate the moment, but welcome to Celtic. That’s the expectation. That’s not going to change.”