On a night when the defensive performance of his team was as wretched as the wet and windy weather which enveloped the Aker Stadium, Deila saw his hopes of Europa League progress significantly undermined with a comprehensive defeat by Molde.
While Ole Gunnar Solskjaer enjoyed the perfect start to his second spell in charge of the Norwegian champions, it is a result which raises fresh doubt over Deila’s ability to give Celtic the status and results they crave at this level.
His team have now leaked an eye-watering 35 goals in 23 European games since he took charge and their vulnerability at the back has simply not been properly addressed.
They trailed 2-0 here midway through the first half and even the lifeline of a Kris Commons goal early in the second half was not grasped as they quickly conceded a third. There was acrimony too for Celtic, Commons responding with very public fury when he was substituted with 14 minutes remaining.
There had initially been no hint of the setbacks which would befall Celtic in the shape of the hosts’ two goals inside the first 20 minutes which put Solskjaer firmly on course for the happiest of homecomings.
If anything, it was the visitors who looked to have adapted better to the treacherously wet conditions which caused spray to fly up from the synthetic pitch with every pass and move.
A swirling wind simply added to the degree of difficulty in producing any cohesive football but a relatively encouraging start by Celtic saw them carve out a decent chance in the third minute, Commons and Stuart Armstrong combining sharply to set up Leigh Griffiths whose close-range effort was blocked.
But that early promise quickly evaporated as Molde stunned Deila’s men with their quickfire double salvo. The 11th-minute opener stemmed from an inexcusably wayward pass from Dedryck Boyata, not the first time the central defender has been guilty of such an aberration in his debut season at Celtic.
He steered the ball straight into the path of Mohamed Elyounoussi who promptly surged forward and played a perfectly weighted pass to Ola Kamara who had found space on the right of the Celtic penalty area.
The striker had time to steady himself and drill a firm, low shot beyond Craig Gordon who was surprisingly beaten at his near post.
The goal provided Molde with a measure of impetus which saw them double their advantage just seven minutes later. It was another goal which exposed Celtic’s consistent inability to observe the basics of defending at European level.
They were unable to clear a corner swept in from the left by Joona Toivio, the ball simply finding its way back to the feet of Molde’s Finnish international. Toivio sent it back across the penalty area where Vegard Forren had been left unmarked by the flat-footed Celtic players.
Forren struck his left foot volley down into the increasingly sodden surface and saw the ball loop beyond Gordon’s despairing right hand and into the corner of the net.
Celtic were unable to find any fluency or bring any conviction to their efforts at a response, with Molde goalkeeper Ervan Horvath not forced into a single save in the first half.
But for a smart stop by Gordon when he turned Elyounoussi’s dipping shot over just before the interval, it could have been even worse for Deila’s side.
They were handed a route back into the contest 10 minutes into the second half by a defensive error from Molde’s Martin Linnes which mirrored the one perpetrated by Boyata in the first half.
Under no great pressure, Linnes sent a pass from the back directly into the path of Commons. The Celtic playmaker reacted eagerly and showed typical composure to loft a smooth finish beyond Horvath from around 12 yards.
It should have been the ideal platform from which Celtic could salvage the situation but instead they switched off fatally at the back again as Molde restored their two-goal advantage immediately from the restart.
Mattias Mostrom was able to gallop into space down the right and his cross found its way to the unmarked Elyounoussi at the far post. His firmly-struck close-range shot slithered under Gordon and into the net.
Kamara should have added to Celtic’s misery when he wastefully sent a free header wide from around eight yards as Molde continued to carry far greater threat in attack.
An evening which had gone horribly wrong for Celtic took another unhappy turn when Commons reacted furiously to being replaced by Nadir Ciftci. As he remonstrated with the bench, the travelling fans also gave vent to their anger as they jeered the substitution. Bitton struck the bar from distance but Celtic were very much second best as they fell to the bottom of Group A.
SCORERS: Molde - Kamara (11), Forren (18), Elyounoussi (56); Celtic - Commons (55)
Referee: V Bezborodov (Rus)