Johansen, 24, has been one of Celtic's players of the season so far, providing the driving force from midfielder thoughout the campaign.
The Norwegian international has only been at Celtic for just over a year, but is a firm fan favourite in Glasgow after a superb season.
Johansen played under manager Deila at Stromsgodset, and was reunited with his former boss last summer when Deila replaced Neil Lennon.
It's therefore little surprise that Johansen has become such a key figure in the Celtic side, and his recent exploits underline his importance.
Johansen has scored five goals in his last 11 games, proving his ability to score from midfield - and in an interview with TV2 back in Norway, he admitted that he doesn't know where his recent goalscoring form has come from.
"I do not know where the goals come from, it must be the new boots or something!" joked Johansen. "I do not actually where they come from. I was a scorer earlier, but it was many years ago."
Johansen started the season in a more defensive role alongside Scott Brown, but has recently been pushed forward into an attacking midfield position - and he has thrived ever since, saying that he loves the role he is playing in under Deila.
"I've got a new role where you will provide goals and assists. It's something I've gotten into my game this year, and I've developed. Therefore, it is fun to see that I get it out on the pitch", he added.
With a potential treble-winning season on the horizon, Celtic will want Johansen's great form to continue - but his recent record could trigger interest from Premier League clubs this summer.