Another European adventure is over for Celtic and having not won a group stage game for the first time in their history, some progress is required if they're to make it through to the Last 16 or even into the Europa League in 2016/17.Despite creditable away draws to Manchester City and Borussia Monchengladbach, the Bhoys were surprisingly let down by their home form and finished bottom of Group C, on three points.
We can't be too harsh on Brendan Rodgers' team, though, as they faced, arguably, the toughest group in the competition with Barcelona, Manchester City and Borussia Monchengladbach being three of the best teams in Europe.
There's a long way to go and the learning process continues, but if Celtic do a few things right between now and the summer then a more prolonged run in Europe is a distinct possibility.
Here are FIVE things that Celtic need in order to progress further in Europe next season...
Ruthlessness
The Bhoys performed admirably in the main across the Group C campaign but there are key moments in each match that they can look back on and wish they had done differently.
Callum McGregor away to Gladbach, Scott Sinclair at home to the Germans, Moussa Dembele's missed penalty in Barcelona and his chance away to Manchester City.
The chances were there for Celtic but they lacked the composure and cutting edge to stick them away. That's the difference at the top level and if they can go into a new campaign with more confidence, perhaps things will work out differently next time.
An easier group!
It doesn't get much tougher than facing some of the strongest sides that Spain, Germany and England have to offer. Celtic were mightily unlucky not to get a more favourable draw with less established opponents.
Barcelona, in particular, seem to follow Celtic around in these group draws - the two sides have been drawn together at this stage of the competition in Celtic's last three Champions League campaigns.
Every Celtic fan would be glad to see the back of them given that they dish out a beating to the Scottish champions more often than not.
A stronger defence
It's no secret that the main problem with Celtic in Europe is their leaky defence. The Bhoys conceded in every Group C match, a massive 16 in total.
Only Legia Warsaw in Group F conceded more, and the Polish side had a similarly tough group.
It may not require a massive change in personnel with Jozo Simunovic and Erik Sviatchenko looking like a partnership that could blossom into something solid. The Hoops were also unlucky to lose Kieran Tierney when they did.
They do need different options in the wide areas, though, to offer better cover and provide first-team competition. If Rodgers can make that one of his transfer window priorities, the Bhoys shouldn't look so fragile come next season.
Make Celtic Park a fortress again
It's become a tradition for Celtic's Champions League to falter based on their away form, but that wasn't the case this season. Earning two draws away from home in the group stages would be a positive for most clubs in the competition.
It was at home things went sour with defeats to Barcelona and Borussia Monchengladbach sinking their hopes of progressing.
The kind of display produced against Manchester City in the 3-3 was never replicated and there was a distinct lack of spirit in the defeats compared to campaigns of the past.
Celtic Park was once a well-known European fortress and in order to progress further in Europe next season, they have to put everything into making sure no team escapes Glasgow with a result.
Another quality midfielder
Scott Brown has excelled in the middle of the park for the Hoops this season, with his tireless performances keeping Celtic going throughout the competition.
His partners have been less reliable, though, with Nir Bitton struggling for form and Stuart Armstrong looking slightly out of his depth against Barcelona.
Armstrong admittedly improved massively away to Manchester City and seems to be developing into the player locked behind potential, but Celtic need another option to compete for his place and push on to a new level.
Signing a quality and experienced midfielder isn't easy but it must be Rodgers' priority in January and next summer if they are to go toe-to-toe with Europe's best and stay in continental competition past Christmas.