Ronny Deila has admitted that Celtic must quickly learn from their heavy loss against Legia Warsaw if they are to progress to the next round of the Champions League.

Despite a positive start in the European qualifier, the Hoops were undone in the Polish capital where they eventually succumbed to a 4-1 defeat.

Deila was critical of his players following the game, but remains confident that they can still pull off a memorable comeback similar to 12 months ago when they trailed Shakhter Karagandy 2-0 after the first leg, before going on to win the tie.

"We started giving the ball way in midfield so many times and mistakes in the back four, some were high, some were low, instead of being together," the 38-year-old manager is quoted as saying by the Daily Mail.

"But what is done is done, we have to learn from this very quick. We got the away goal and we still have a chance. It is possible to win 3-0 again - like we did last year in the play-off - and with the help of the supporters we will do everything we can to do that.

"But we have to learn from this week. We need a whole different attitude and discipline in our play."

Deila took over at Celtic in June after leaving Norwegian club Stromsgodset.