Ange Postecoglou has conceded his squad rotation didn't help Celtic as they fell to defeat against Rangers.
The Parkhead boss was hoping to achieve an unbeaten record against Rangers this season but watched his side falter to a 3-0 loss.
Postecoglou had made a raft of changes to his side with Alexandro Bernabei, Yuki Kobayashi and Anthony Ralston in a much-rotated backline.
Liel Abada was given the nod on the right flank with Oh Hyeon-gyu starting as the central striker in place of Kyogo Furuhashi.
For Postecoglou, the changes may well have been a factor in the defeat as he also cited the opposition and Ibrox atmosphere.
"There is probably a number of reasons," said Postecoglou. "But credit to Rangers and obviously you are facing a difficult opponent at their venue and the amount of changes I made probably didn't help in terms of the guys lacking a little bit of sharpness.
"At the end of the day we just weren't good enough."
Pushed on performances from fringe players at Ibrox, he added:"As I said they were a bit off it today and that is part of the experience of playing for this football club.
"It's relentless and you do not get any easy introductions. We have thrown guys into derbies for pretty much their first game. This is how you understand what it is to be a player at this football club."
Asked if anything more could be learned in defeat after such a successful season, Postecoglou said: "I learn all the time mate, you never stop learning."
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