European away games can do that to a man.
Celtic's return flight from Slovenia landed almost as dawn was breaking yesterday and the manager was soon back on duty, facing the media to promote the Maestrio Charity Match between Paul McStay and Rio Ferdinand's teams at Celtic Park on September 7. Deila barely slept after losing 4-1 away to Legia Warsaw and he admitted he hadn't had much rest after Maribor either.
The circumstances, of course, were entirely different. This week's 1-1 draw put Celtic on the way to the Champions League group stage.
"I didn't get much sleep but I woke with a better feeling than I did the last time," he said, with wry understatement. "But it's just the first half of the tie. It's nothing to celebrate. We went away and got a good result and we deserved it. It is important now to concentrate on Inverness."
Deila is likely to pick a different Celtic team at Inverness tomorrow without regarding it as a weakened one. The champions' trip to Caledonian Thistle comes between two of the most significant fixtures of their season, the away and home play-off round games against Maribor. Resting key men in the Highlands in order to protect them for the Slovenians' visit on Tuesday would be entirely sensible.
"We'll see what we do, but that's one of the opportunities you have at Celtic. The advantage that we have is a very big squad of 25 players who can play the top level in Scotland. I think there will be some changes [in Inverness], yes.
"I think the squad is big enough for that. It's important to prioritise in modern football but it's also important to give people a chance, to keep up the motivation in the group. If we play every week, three times a week, especially when it is three games in six days, you need to use your head. We're going to be in Europe now until Christmas.
"We're going to have only one week when we are only playing one game. That's different for me as a manager."
Celtic's season is only seven games old. Incredibly, it has already rushed to a point in which Callum McGregor is the man of the moment - he had not made his debut two months ago - while Kris Commons is the subject of debate and conjecture after being dropped on Wednesday night. Deila wanted a midfield which would offer his defence more protection in Slovenia, but Commons' form had previously made him sacrosanct.
Had Deila spoken to him? "I talk to players. When I spoke to him before I announced the team he understood that we wanted to play another system. He's a team player. It's no problem. He's a very important player in the group, off the pitch and on it, but this time we wanted a more defensive midfield so we left him out."
Commons scored 31 times last season and has one in the current campaign. McGregor had never scored before July, and now he has four. "He's just a quality player," said Deila of the 20-year-old. "He's fantastic. He still has a lot to improve, but what I like is that he works two ways. He is not only offensive, he is also doing the defensive job. If you are going to play with three or four in the midfield, you need wingers who want to work hard, especially in Europe. That's the target. That's how we want it."
McGregor has been the chief beneficiary of Deila's arrival, a player who went from obscurity to centre stage under the Norwegian and rewarded him with three goals in consecutive Champions League away games. Deila simply purred about him yesterday: "He's well educated. He has fantastic technique and balance. The touch is unbelievable. He's a goalscorer.
"When you see him shooting in training you understand why he scores goals because he has unbelievable quality in finishing."
Proclaiming a great young Celtic talent on the back of European exploits is an uncertain business. Tony Watt's winner against Barcelona feels like it happened only yesterday. The world was at his feet, but his attitude and application failed to impress and he was unceremoniously sold. Deila made no criticism of Watt yesterday but it was clear that he regarded McGregor as a more impressive figure.
"People are different. McGregor is never going to take off in that way, he's training hard every day, he's a calm person. I have no worries for him. It's hard to say how much he can achieve in the game but now he's at a high level. He can reach a high international level too. I think he can be even quicker and even fitter but he needs more experience.
"Could he handle the Champions League group? Why couldn't he do it there? If the others can do it, he can do it as well."