Celtic’s qualification hopes from Group A suffered a huge blow after a hugely disappointing defeat to Molde.
Despite a bright start, the Hoops lost two goals from defensive blunders and failed to recover from the setback.
Ola Kamara put the hosts in front before Veggard Forren inflicted further punishment on the Scottish champions’ rearguard volleying home from close range.
Kris Commons handed Celtic hope with a deft chip but it was immediately extinguished by Mohamed Elyounoussi, who squeezed the ball in from a tight angle.
It leaves the Scottish champions bottom of Group A and plenty of work to do progress from the group with the Norwegians flying high at the summit.
Celtic made an encouraging start as Leigh Griffiths threatened early on but soon found themselves trailing by a couple of goals in quick succession.
A perennial problem in Europe for the Hoops has been their propensity to concede soft goals and they did it again in Norway.
Molde hadn’t been seen as an attacking force beforehand but they were gifted an opening when Dedryck Boyata needlessly gave possession away to Elyounoussi.
The Moroccan-born winger, back from suspension, scurried forward, played in Kamara who slotted past Craig Gordon at his near post.
Celtic were unable to cope with the counter-attacking style of the Norwegians and they soon doubled their advantage.
Joona Toivio engineered space down the left, crossed the ball into Forren, who volleyed in the second after drifting off his marker Izaguirre.
New Molde boss Ole Gunnar Solsjkaer must have allowed himself a wry smile at what was unfolding in front of him, while it was a chastening experience for Deila back in his homeland.
And it could have been worse for Deila’s side had Gordon not shown good reflexes to tip over Elyounoussi’s cross-cum-shot just before the break.
Celtic’s play was pedestrian in the first half but a couple of Nir Bitton efforts after the interval suggested an increased sense of urgency.
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And Commons thought he’d given his side a lifeline when he capitalised on a slack clearance from Linnes before cooly chipping the ball over Horvath to halve the deficit.
But, infuriatingly for the visiting support, Molde restored the two-goal cushion within a minute as Elyounoussi slid in at the back post to squeeze the ball beyond Gordon.
Kamara could have made it four with a couple of efforts on the counter, while Commons’ deflected effort had Horvath concerned.
But that proved to be the last action for Commons, who was seething at the dugout at being replaced by Nadir Ciftci.
Bitton cracked the bar with a long-range effort late on but ultimately it was a miserable night for the Hoops.