Liam Henderson has been on loan at Rosenborg from Celtic since March.
Henderson joined the Norwegian side on loan in March, and it was a move that Deila encouraged him to make.
The 19-year-old says that Deila talked him into making the switch, and he is glad that he did after embracing the opportunity to experience life away from Parkhead.
"From the outset, he told me to come here, get experience, play games," he said.
"Rosenborg play near enough the same way as us, so I'll be ready to come back for pre-season and be looking to play. He gave me a good message and that filled me with confidence. I've taken it in my stride and I've enjoyed it.
"The aim for me and the manager is that I come back fitter, faster, an all-round better player."
Henderson's loan move was a slight surprise for many Celtic supporters, as he seems to have the ability to perform a role for the first-team despite his lack of experience.
However, Deila obviously felt his development would be best served by getting regular competitive action in a new environment, and so far the loan move has worked out well for all concerned.
Henderson has become a key part of Rosenborg's side and has scored three goals during his brief time with the Scandinavian club.
It is a period that will have taught him a lot about himself and he will be hoping to return to Celtic an improved player, as he looks to break into the Bhoys senior side next season.