Deila said: “We are conceding goals too easily. On Thursday, they had two chances and a shot from distance that hit the bar.
“The two chances were one v one in the box that we have to deal with. It was the same with Fenerbahce. It’s too easy and when you do things like that in Europe you get punished.
“I was angry and very disappointed. It’s a lack of determination. That is something that Scotland is known for and what KT (Tierney) showed on the pitch, that’s real Scottish mentality. When you go back 20 years and think of those players – that’s what we need.
“That was at the bottom of it. That’s something we need more of. We need some character, leadership and determination.
“There were 10 men in the box at the second goal, so it’s not about that. I don’t see teams cutting through us to make clear chances. I don’t see that.
“We need more physique there. We need more determination in the box at set-plays.”
Speaking of his future, Deila said: “This club has shown they stand by their managers when they have a hard time in Europe. That’s what I expect, too.
“ I’m very confident we will turn it around and get improvements in the last two games, which is one thing, but also next year.
“We cannot fight the big teams. But we can beat Molde, Malmo and Legia Warsaw. That’s my target next year when we come to the Champions League.”