Celtic boss Ronny Deila has admitted that he was "unbelievably disappointed" by his side's performance during their 4-1 defeat at the hands of Legia Warsaw in the Champions League.

The Norwegian conceded that his team lost composure after their hosts equalised through Miroslav Radovic, and questioned the commitment of his players.

"I think we started quite well and got the first goal and then we conceded an easy goal. After that, we lost our heads," BBC Sport quotes him as saying.

"We lost the ball in the centre of the pitch so many times and the back four didn't stay together. They got easy chances, and then there was the red card and after that it was a totally different match.

"We started the second half okay but again we weren't together as a team in many situations. Worst of all is the commitment, the energy. We needed much more energy in the game. We did not stay together for 90 minutes, that's what concerns me the most."

Callum McGregor's early goal gives Celtic slender hope of reaching the next phase of the competition ahead of next week's second leg at Murrayfield.