A 2-1 home defeat to Ajax ended the Hoops’ Europa League campaign is over with one group game still to play against Fenerbahce next month.
But Deila was in defiant mood and claimed his players are “very close” to being a threat in Europe.
The Norwegian said: “We buy talent, players who can be Champions League players. Nobody comes in and is a Champions League player in 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.
“It is very hard to bring in a player who has played a lot of Champions League games, that is a 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.”
Deila also denied the season will now fall flat. He insisted: “It’s not like we’re going to close down until next August.
“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, 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.