What must still be perplexing him, however, is how the club he now manages can be embroiled in such a topsy- turvy season.
Indeed, it could be argued it is back to front.
Anywhere else, the most important games come towards the end of the campaign, when the silverware is handed out.
Here, the Hoops' key fixtures are all front-loaded, and define their entire season as it is when the gold is on the line.
A case could easily be made that the six steps towards the Champions League group stage are a season within a season, and more important than the main event itself, given how much influence success or failure in the qualifiers and play-off matches carry.
This year, though, the opening two SPFL matches can be included in the highly-important category.
It's not because they will determine whether or not the Hoops can march towards four-titles-in-a-row.
Even defeats to St Johnstone in Perth tonight and Dundee United after the league flag is unfurled by Fergus McCann at Celtic Park on Saturday would not alter the bookies' view that Deila's side are 66-1 on favourites to retain their crown.
It is the timing of these two domestic games, coming after the defeats - on the pitch, at any rate - to Legia Warsaw and before the Champions League play-off against Maribor a week tonight, which attaches to them so much more significance.
Deila has 180 minutes to rectify what was so clearly wrong against the Polish champions before he sends, ostensibly, the same side - with the addition of teenager Jason Denayer and pacy Aleksander Tonev, but minus Fraser Forster - out to face Maribor in Slovenia.
Players need to have their damaged confidence repaired, fans their fractured belief restored and the recovery must start at McDiarmid Park, where Deila's own reaction to what has been a baptism of fire in Europe will be under scrutiny.
The Norwegian needs a positive response and result, and said: "It's been a very strange start.
"You go straight in and suddenly you play the most important games in the whole season.
"It is going quick, and there are a lot of things to get into your head.
"I have had pre-season matches, and Champions League matches.
"Now the league is starting, and these are now the important matches to use to get good results, develop the squad and the team in the right direction.
"So, I'm really looking forward to this game tonight.
"We have to be up for the game and get our tempo up in the match so we can create more chances than we have done in the past two games."
If the players available tonight could match the speed with which captain Scott Brown is racing back from his hamstring tear, there would be no chance Saints could live with them.
The manager reports he is having to hold the effervescent midfielder back in his rehab to avoid a setback.
But Brown's return to action could be just a month away, good news for club and country.
Even if he is not yet able to play, Brown is fulfilling his captain's duties, including welcoming new faces to the squad.
The latest are Tonev and Denayer, two loan captures from Aston Villa and Manchester City, respectively.
Deila is delighted to have added what he considers to be real quality to his squad, with 19-year-old defender, Denayer, in particular, exciting the manager.
If pushed, the Norwegian would class the teenager in the £10million-plus bracket, a fee which - even if there was an option to buy, which there is not - would take him well out of Celtic's reach.
They can, however, give him first-team football, and get the benefit of having a genuine rising star in return.
Deila said: "He's a player Manchester City wants to get out to gain experience.
"They think he can break quickly into their team."
He went on: "Denayer has the level so can go straight into our team and perform at once.
"Jason can also be a really good sign for young players here, when they see this level from a young, top, international player, his attitude and everything.
"So, it's a double bonus."
Deila is confident the Hoops fans will be impressed, and said: "I've watched Jason in many games because we have, in my old club, a co-operation with Manchester City.
"He's a very good, very talented player, the kind who will suit us, and the way we want to try to play.
"It also gives us good competition in defence."
That's a clear attempt to defuse the belief that Denayer's arrival will allow Virgil van Dijk to move nearer the exit.
Deila is confident the Dutchman wants to stay, for a while yet, anyway, and add to his medal collection and European experience.
"I think we're done in this window," said Deila in reference to selling their best players, before adding the ubiquitous caveat, "But, again, you never know in football. It's about money.
"So far there has been no interest, and he is important for us in the Champions League and in the league as well."
A slight injury means Tonev will need to wait at least until the weekend to show he is the player Celtic tried to sign from Lech Poznan and not the shadow figure who operated in the background at Aston Villa last season.
Deila has sensed the Bulgarian is eager to prove his critics wrong and said: "He can play No.10 and in the midfield, but I see him more as a winger. He has the qualities we are looking for.
"He's has not been playing much at Aston Villa, and this is a new chapter for him to get his confidence up and get back to the levels he was at with Lech Poznan where he did very well."