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Boss Ronny Deila saw Celtic crash out of the Europa League then claimed "small details" will make side ready for the Champions League next season.
A 2-1 home defeat against Ajax kept the Scottish champions bottom of Group A with two points from five games making next month's trip to play Fenerbahce in Istanbul a dead rubber.
Hoops returning midfielder Callum McGregor, only starting due to a midfield crisis, gave the home side the lead and some hope in the third minute with a drive.
However, Arkadiusz Milik levelled in the 21st minute and in the 88th minute substitute Vaclav Cerny's breakaway winner confirmed the Hoops' exit from the tournament with a trip to play Fenerbahce in Istanbul next month remaining.
But Deila, who has spurned three chances to reach the Champions League since becoming Celtic manager, remained defiant, saying: "We buy talent, players who can be Champions League players.
"Nobody comes in and is a Champions League players the first game.
"You have to develop them through time and we are going to be ready next year, that is the message to all the fans and that is the task that I and everyone in this club has.
"It is small details, you have to be good in small details to win games.
"That is very close but it is not good enough right now.
"I see it small details. If you see the big picture you are also going to see that.
"It is very hard to bring in a player who has played a lot of Champions League games, that is different level but we have created a lot of Champions League players and we are going to do that in the future as well.
"It is important that we use the January transfer window well and the summer one as well of course."
With Celtic still top of the Ladbrokes Premiership and in with a chance of a domestic treble, Deila was keen to stress that the season was "not over".
"It's not like we're going to close down until next August," the Norwegian said. "We are going to keep going domestically. We are leading in the league by six points and are still in every tournament.
"I think it's very wrong to say the season is now over.
"We are very disappointed. I am very disappointed that we are not through to play European football in February. But it's done now and we can only look forward.
"This makes me have a lot of energy to bounce back which I have done many times in my career. I will do it here as well."
Deila was without suspended midfielders Nir Bitton and Stefan Johansen with skipper Scott Brown out for up to 12 weeks with a knee injury while Kris Commons was out again with a combination of a hamstring injury and illness.
The former Stromsgodset boss now looks as if he will be without Charlie Mulgrew for the trip to Inverness on Sunday.
The Scotland international came on as a second-half substitute for Tom Rogic to make his first appearance in over two months after recovering from a thigh problem but hobbled off before the end with another injury.
Deila said: "He pulled his muscle again. I don't know if it is the same injury again. It seemed more advanced than just a cramp.
"When you can't run, it's better he is not there."
Celtic striker Leigh Griffiths expressed his disappointment at his own performance on his official Twitter account.
He said: "I can't be more apologetic than I am right now. My performance was Simply SHOCKING and ultimately its cost us dearly."
Deila, though, was in forgiving mood saying: "Of course he had chances, but he scores a lot of goals for us.
"He had the chances and that's a positive thing.
"He will score more goals in the future. That's the way football is."