On the day the Parkhead club lifted the Premiership trophy and celebrated their fifth successive title win, they completely dismantled a shell-shocked Motherwell outfit to allow Deila to sign off in style.
There were seven different goalscorers in a display of power, precision and purpose from Celtic. It was also a day when a little piece of history was made as Jack Aitchison – just 16 years and 71 days old – became Celtic’s youngest player and scorer when he came off the bench to net with his first touch of the ball.
It was an enticing glimpse of the future for Celtic, a future which will not involve Deila. But it set the seal on a performance which allowed him to leave the club with his head held high, which was the least he deserved.
Having formed a pre-match guard of honour to applaud Celtic on to the pitch, Motherwell were simply played off it.
Before goalkeeper Connor Ripley’s afternoon turned horribly sour, it was only his early exertions which prevented the hosts making the breakthrough sooner than they did.
Moving the ball with pace and invention in the attacking third of the pitch, Celtic created a succession of clear-cut openings. Tom Rogic shot tamely straight at Ripley in the seventh minute, then the goalkeeper reacted smartly to keep out a close-range effort from Ryan Christie who was the surprise replacement up front for suspended top-scorer Leigh Griffiths.
Ripley then made a magnificent, leaping save to touch over a dipping 20-yard shot from Rogic and maintained his level of defiance when he smothered another attempt by Christie, who had been sent clean through by Mikael Lustig. But Ripley had no answer to Celtic’s 21st minute opener which provided a moment to cherish for Kieran Tierney. Scotland’s Young Player of the Year, whose impressive emergence this season is one of the most positive legacies of Deila’s time in charge, cut in from the left before burying a low right-foot shot beyond Ripley into the corner of the net.
It was the prompt for a meltdown in the Motherwell backline as Celtic trebled their lead within another eight minutes.
Rogic made it 2-0, tapping his tenth goal of the season into an empty net after Stuart Armstrong had struck a post after playing an incisive one-two with Christie on the edge of the penalty area.
Ripley, now looking as rattled as he had appeared assured earlier, then allowed a Rogic cross-cum-shot to squirm under his body, his blushes spared this time by Marvin Johnson’s clearance off the line.
But there was nowhere for Ripley to hide when Celtic added their third goal in the 29th minute. He completely misjudged Armstrong’s inswinging corner from the left, presenting Lustig with a free header which the Celtic captain powered home from close range.
It should have been even worse for Motherwell before half-time as Christie contrived to perpetrate one of the misses of the season. Left with an open goal after Ripley had parried a Rogic shot, he screwed his shot off target from around six yards out.
McGhee made a double substitution at the start of the second half, replacing Luke Watt and Lionel Ainsworth with Joe Chalmers and Kieran Kennedy, but there was no respite for his side as Celtic continued to cut through them relentlessly.
Armstrong made it 4-0 six minutes after the restart, taking one touch to control a Lustig cross on the edge of the penalty area before smashing a superb right-foot shot high beyond Ripley’s right-hand into the roof of the net.
The final whistle simply couldn’t come quickly enough for Motherwell but there was further pain for them to endure before they could slink away for their summer break.
Patrick Roberts scored what is becoming a trademark goal for the on-loan Manchester City winger, drifting in from the right and spearing a low left-foot shot into the far corner of the net for Celtic’s fifth of the afternoon.
Number six followed in short order, Christie atoning for his first-half howler as he scored his first goal for the club, finishing neatly from around 16 yards after being set up by Rogic.
If this was the stuff of nightmares for the visitors, it was dream come true material for young Aitchison as he made his stunning entrance into the Celtic history books. Just three minutes after replacing Rogic, he made it 7-0 with a coolly taken goal as he latched on to Christie’s pass and guiding a left-foot shot beyond Ripley. He eclipses both Mark Fotheringham as Celtic’s youngest first-team player and Paul McStay as their youngest goalscorer.
Craig Gordon’s presence proved not completely unnecessary for Celtic, the ‘keeper finally making his only save of the day to deny Morgaro Gomis a late consolation for the visitors.