As the minutes ticked down on the deadline for registering a wild card player for the ties against the Slovenian champions, the difficulty securing a work permit for Mubarak Wakaso left the Celtic manager disappointed.
The Ghanaian had earlier passed a medical in Moscow and was due to fly into Maribor late last night. But, without the vital piece of paperwork, Deila accepted he would not be eligible to play in the play-off ties.
Celtic plan to proceed with the year-long loan deal from Rubin Kazan, when they are eventually granted the work permit for the 24-year-old who has played 19 times for Ghana, but, crucially, not in 75% of their recent internationals.
"It's going on," said Deila of the behind-the-scenes activities. "But it's hard to get the paperwork and things together. I'm not 100% sure, but I think it's going to be hard to have him ready for the game against Maribor."
Ironically, paperwork was also at the root of the good news which offset this disappointment, even if it did leave Celtic looking a little sheepish.
Efe Ambrose did not travel with the squad when they flew out to Maribor yesterday because Deila was under the misapprehension the defender was still serving a ban imposed for his red card in the first leg of their qualifying tie against Legia Warsaw.
The manager had previously stated the Nigerian had been given a two-game ban, the first of which he served when he sat out the controversial second-leg tie against Legia at Murrayfield. However, it was brought to Celtic's attention when they arrived in Slovenia that the suspension was only for one match, and travel arrangements were urgently put in place to get Ambrose out to Maribor today.
Given the problems encountered by Legia which gave Celtic a second chance in this competition, it was an embarrassing error on their part. "There was some complication with communication problems about if he was ready or not," explained Deila. "We didn't think he was ready because he got two matches. But, in the end, it is one match, and he's coming out. I'm very happy about that because we need defenders."
Now Deila must assess Ambrose's condition and decide if it is too much of a gamble to include him in tonight's starting XI. Whichever players are selected - James Forrest, Adam Matthews and Aleksander Tonev are injured - Deila is confident they will be much better prepared to achieve a positive result than they were when they faced Legia Warsaw.
However, while personnel and form may change, the manager maintains the fundamentals remain the same.
He said: "If we perform well, we'll get our results. If we don't do it, we will not reach it. So the performance has to be much better than it was against Legia. We also know that if we come away from here with a good result, we have the crowd behind us at Celtic Park and everybody knows how much that means.
"We have improved, are more prepared, and I have a good feeling we can give a good performance and get a good result to take to Glasgow."