Having returned from Slovenia with a 1-1 draw to put themselves in the driving seat for a place in the Champions League, the Hoops boss knows one of his biggest challenges will be managing expectation.
With the away-goal advantage, his side is tantalisingly close to booking a place in Thursday's Group Stage draw - and banking the £15million that comes with it.
But, perhaps still scarred from the disappointment of how poorly his side played against Legia Warsaw in the previous round, Deila refuses to be lulled into a false feeling of security.
"The job is, of course, not done," said the Norwegian, in a steely tone which makes it clear this is not open to debate.
"We are playing against a very good team and we are doing everything we can to be as prepared as we can possibly be. I have my team in my mind. I have thought about it for some time."
Which is why the side which lost 1-0 at Inverness at the weekend showed 10 changes from the one which started in Maribor.
Deila knows what to expect from the Slovenian champions, and will ensure his players do, too.
He didn't see anything in last week's first leg he did not already know and said: "We had prepared well for the game in Maribor. We had the right match plan."
That in-depth analysis of the opposition includes special video dissection by Haakon Lunov, taken during the game and relayed to the manager at half-time and full-time.
A minute before the break in Maribor, Lunov raced from his vantage point at the back of the main stand right round the stadium to the away dressing room in time to show Deila what he had noted in the opening 45 minutes of the first leg tie.
It's information the manager can then use to tweak his side or focus on weaknesses in the opposition.
Deila will again use everything available to him tomorrow night, and makes no attempt to down play how pivotal this result will be in their entire season.
"It is an unbelievably important game for us," said the man who is aiming to get involved in the Champions League for the first time in his career as a player or manager.
"So we are going to give everything. Then we will have a good chance."
Deila knows that success tomorrow night will soon remove any disappointment created by the defeat at Inverness, which sees the Hoops drop to fifth in the table.
He believes time will show he made the right call with his team selection and said: "We have to see it over the longer perspective.
"We were thinking about tomorrow's game, but we still wanted to win against Inverness.
"We got very passive. But when you have a lot of young players on the pitch, you need men to open up these spaces.
"It's going to be a learning experience for everybody, and we have to take this with us and think about the next game."