Celtic manager Neil Lennon has lamented his side's inability to take their chances against AC Milan on Wednesday.
The Scottish giants suffered a 2-0 defeat to the Italian club at the San Siro in their opening Champions League Group H game.
"We had good chances tonight and that will be the one regret," BBC Sport quotes him as saying.
"We were in good spirits coming into the game, it heightens the disappointment by playing so well. Our performance was of a very high standard.
"We have Barcelona coming up and they're a different animal. I've told the players to hold onto the disappointment of tonight and take that into the game in two weeks' time."
Christian Zapata and Sulley Muntari scored for Milan in the final 10 minutes of the match.
