Celtic have missed out on the Champions League group stages for the first time in three seasons under Brendan Rodgers.
A 2-1 defeat by AEK Athens in Greece saw them bow out 3-2 on aggregate and drop into the Europa League play-offs.
Here, Press Association Sport examine some of the factors behind their early exit.
Absence of Boyata
Belgium defender Dedryck Boyata was handed extra time off after helping his country to a third-place finish at the World Cup, but Rodgers claimed he had effectively downed tools ahead of the second leg in Greece, where he would have played if available.
Boyata claimed he was injured, after his agent insisted he would not play if 95 per cent fit after being angered by the club knocking back a significant offer from Fulham.
But Rodgers insisted that Boyata had been fit to play and pointedly stated they needed all the help they could get to qualify.
Inexperience At The Back
Boyata’s absence came on top of suspension to Kristoffer Ajer, who had started the previous five qualifiers in central defence, but had been guilty of a lack of awareness when AEK equalised in Glasgow.
Celtic started with 21-year-old Jack Hendry and Jozo Simunovic in central defence in Athens and the defensive frailties which have cost them in Europe in recent seasons returned to haunt them.
Rodrigo Galo converted a cutback from a penalty box which was crowded with Celtic players inside six minutes and Marko Livaja was unmarked as he headed the crucial second.
Lack Of New Signings
Celtic’s only summer signings, striker Odsonne Edouard and second-choice goalkeeper Scott Bain, were at the club last season and Rodgers gave a clear indication last week of his frustration at the club’s failure to close more deals.
A centre-back seemed a priority with January signing Marvin Compper perennially injured, but the only defender moving went the other way as Erik Sviatchenko departed.
The failure to sign John McGinn from Hibernian appeared to shine a light on dealings – Celtic had three bids rejected before finally meeting the asking price when the midfielder had already decided to sign for Aston Villa after Steve Bruce made his move less than 72 hours before the English transfer window shut.
Key Players Go Missing
Edouard missed out in Athens after picking up a knock and Moussa Dembele came off the bench after four weeks out with a hamstring injury.
Leigh Griffiths started and missed a decent chance which he might have expected to score if he had been sharper, after missing much of July with a thigh strain.