Here Press Association Sport's Andy Newport takes a look at where he struggled with the Hoops:
PERIOD OF DOWNSIZING
It cannot be forgotten that Deila took over at a time when the financial ambition of the club had been drastically scaled back - it was the very reason he got the job
Neil Lennon quit after becoming disillusioned with the Parkhead board's thriftiness, while top targets like Roy Keane and David Moyes baulked at the meagre budget they would have had to work with
The 2012 financial implosion of Rangers left Celtic in a difficult conundrum - stick to spending big in a one-horse race and hope to get the cash back by making it to the Champions League, or take a more prudent approach before only releasing funds once a group-stage slot had been confirmed
Chief executive Peter Lawwell opted for the latter
EUROPEAN MISADVENTURES
With so much riding on qualification to Europe's biggest competition, Deila was under pressure from the off
He had only been in the Hoops hot-seat for eight weeks when Celtic were dumped out of the Champions League following a 6-1 pounding from Legia Warsaw
Even when his side were given a second chance of making the money-rich group stage after the Poles were thrown out of the competition for fielding an ineligible player, they slumped once more against Maribor
They did make it to the last 32 of the Europa League before losing narrowly to Inter Milan but another Champions League failure against Malmo in this year's qualifiers only increased the doubts about Deila's leadership
H e was lucky to survive past Christmas after going through the Europa League group stage without a win
POOR RECRUITMENT
Without the Champions League bonus money to fall back on, it was up to Deila to show his nous in the transfer market but few of his signings made a positive impact
After insisting he would not bring in loan players, he was then forced to borrow Manchester City pair Jason Denyer and John Guidetti after missing out on his first-choice picks
At least they worked, though, unlike permanent additions such as Stefan Scepovic, Gary Mackay-Steven, Stuart Armstrong, Dedryck Boyata, Saidy Janko, Nadir Ciftci, Scott Allan, Ryan Christie or Colin Kazim-Richards - who have either been outright flops or made little impression
As things stand, the badly balanced Celtic squad has 17 midfielders but only one reliable striker in Leigh Griffiths
MAN-MANAGEMENT
The Celtic supporters lapped up the 'Ronnie Roar' when things were going well under Deila but things did not always appear so rosy with some of his players
Kris Commons' astonishing outburst when he was substituted during the Europa League defeat in Molde earlier this campaign revealed his fractious relationship with his manager
The former Scotland forward is arguably the most dangerous weapon on the Parkhead books but Deila did not seem to trust the 32-year-old
Motivation also appeared to be a problem
Compared to the fired-up Rangers squad on Sunday, the Hoops laboured through what many felt was their most important match of the season
HAMPDEN HORROR SHOWS
With his European record so shambolic, Deila could have taken the pressure off himself on the domestic front by landing a treble
Only two Parkhead bosses have managed the feat before - Jock Stein and Martin O'Neill - so it is not a given
However, the 40-year-old had his chances
After landing the League Cup last March, Deila's side have failed to win any since
Against Inverness in last term's Scottish Cup semi-final they were hard done by as the officials failed to spot Caley Thistle defender Josh Meekings' goal-line handball
But they were again lacklustre against County in the last four of this se ason's League Cup and the penalty shoot-out defeat to their Old Firm rivals on Sunday was the final straw for many Celtic supporters
Source : PA
Source: PA