“When have you seen him like that? I haven’t seen him even near to what he is now.
“I said in the past that he needs time because he was down for so long injury-wise and it takes time to get back again. Now he has been injury free for eight months.
“He has had small things, but nothing major and he has been consistent in training.
“Before in the games he played, he was giving me heartache because we didn’t see the intensity we needed to see. He was also afraid to get injuries.
“He had to get over that boundary to understand that nothing was going to happen and he could give 100 per cent. The development he has had over the last month has been tremendous.
“When he gets 100 per cent in training and in matches then we have a top player and he can also do it at international level.
“Now we have control of him, but we are not even close to being there. In my opinion he is fifty per cent of what he can be. Now we just have to keep on building but that takes time.”
Deila also praised 18-year-old European debutant Kieran Tierney, who came in at left-back for the suspended Emilio Izaguirre.
“He learns quickly and he is curious to learn all the time. He is very strong mentally. He is very tight defensively and that’s what I like.
“We always get full-backs now who are very good offensively, but a lot of them lack ability defensively and when you are a defender you are first of all a defender.
“I am looking forward to working with him more in the future. Yes, he can be Emilio’s replacement in time. That’s what everybody is hoping for.”