According to Callum McGregor's comments on Celtic’s official website, Ronny Deila told the Bhoys’ squad that their European exit was down to fine margins.
Celtic have crashed out of the Europa League, after failing to win any of their five group stage matches.
Two defeats against Molde were hugely damaging, before a loss to Ajax in their last European outing sealed their fate.
Celtic now face Fenerbahce on Thursday evening with nothing to play for, but McGregor says Deila has encouraged the squad to learn from that experience.
“As the gaffer says, it’s the small details that cost you in European games – we really need to be switched on for defensive and attacking set-pieces,” McGregor said. “That’s something we will look at for the next campaign.”
Celtic’s early exit in Europe has put the pressure on Deila, as he has failed away from domestic competition in both of his seasons at Parkhead.
The Bhoys have dropped out of the Champions League in the qualification stages for two seasons running.
They did make it to the last-32 of the Europa League last term, but this season’s showing has been a serious step backwards.
Celtic will, therefore, be playing for pride against Fenerbahce in midweek, but the Turkish side could still qualify – if they are able to pick up a point.