Celtic boss Ange Postecoglou put it simply by admitting "we are not at this level yet", after his side's Europa League dream was ended by Bayer Leverkusen.
A potential glory night under the Parkhead lights against Real Betis was wiped off the slate by a late show in Germany, as the Bundesliga big boys secured a 3-2 win.
There has been plenty to like about Celtic this season on the continent but 13 goals conceded in five group stage games shows where the Australian must seek improvements.
It would have been a case of putting the travel bag away in years gone by, however, more European adventures lie in wait as the Parkhead side drop into the Europa Conference League.
UEFA's third tournament has offered teams from less fashionable locations to blossom.. and it is working out well.
Roma and Tottenham were the biggest names aboard the maiden voyage but both Jose Mourinho and Antonio Conte are sweating about winning the group stage.
That is on Celtic's agenda because they will face one of the eight runners-up over two legs in February, with the group winners taking safe passage into the last 16.
Record Sport runs the rule over the sides who lie in wait as things stand with only one matchday remaining before the draw in Nyon on December 13.
Maccabi Tel Aviv
Tel Aviv are the only side locked into second place.
They have been good but not as good as LASK Linz, the side who saw off St Johnstone, and they can't go up or down on matchday six.
Tel Aviv are having a wonky season in the Israeli top flight with only three league wins out of nine games.
They are capable but remain managerless after Patrick van Leeuwen paid with his job due to their domestic disputes.
Maccabi will hope they are in a good place comes the knockouts but they aren't enjoying a vintage campaign.
Flora Tallinn, Partizan Belgrade or Anorthosis Famagusta
Group B is the only one where three teams remain in the mix of finishing second. Gent have secured top spot and a trio are jockeying for position in an ultimate competitive group.
Logic would suggest Partizan Belgrade would offer the most resistance, however, Tallinn have been excellent in this tournament and their win over Belgrade on matchday five was a blockbuster result.
Famagusta were Rangers sparring partners in the 90s and the current side will aim to secure shock progression with a win in Belgrade.
Bodo/Glimt or Roma
What would you choose? The rising Norwegian disruptors with a knack for exciting football or Jose Mourinho and a return to the Stadio Olympico?
Bodo/Glimt and their coveted manager Kjetil Knutsen have been bubbling under but they have gone mainstream since their stunning 6-1 win over the Special One's side back in October.
But Roma can still win the group, despite that sorry night in Norway, and one of these two will be among the eight in the mix for Celtic.
A reunion with Mourinho offers a certain romance for Parkhead punters who are still smarting over that UEFA Cup Final defeat in Seville.
UEFA's third tournament would have a marquee match-up if the Romans and Celtic are matched up.
Randers or Jablonec
Celtic have previous history of double dunting on the same opponents in Europe in the same season - with UEFA offering more trap doors than Pat Sharp's Fun House.
Brendan Rodgers and Neil Lennon both had a pair of doses of Cluj and Rosenborg in recent seasons.
Jablonec were dispatched 7-2 on aggregate in Europa League qualifying but the gritty Czech side are in the mix to get out of the group stage.
Danish side Randers (the songs will write themselves) are one point ahead but a trip to Holland to face Alkmaar is packed with danger - even if the other side Celtic defeated in Euro qualifying this season are entrenched as group winners.
Slavia Prague or Union Berlin
The write-up on Slavia this season is they are a shadow of the side which dumped Rangers out of Europe last season.
The racism from Ondrej Kudela that engulfed Ibrox was vile beyond words but, purely based of football, Slavia may be a decent foe.
Union Berlin might be a bit of a dream tie for travel hungry Celtic fans, Germany is made for going to watch your team and the upstarts in the capital have a cracking little arena with the Försterei housing 22,000 people.
This group will go all the way.
Slovan Bratislava or PAOK
Slovakia or Greece could be on the Celtic flight plan next year with both teams knowing they are one big result from the knockouts.
Bratislava will travel to Copenhagen but PAOK will fancy their chances against Lincoln Red Imps on matchday six.
Neither side will make it easy on Celtic, or whoever they face, but this might be high on the list of potential opponents - both appear beatable.
Vitesse or Spurs
A draw that might be best avoided.
Antonio Conte will have his Tottenham stars up to speed come February but they might be out of Europe by then.
They'll need a win at home to Rennes to make sure of their place in the knockout stage with Vitesse ready to pounce if they slip up.
Conte was crestfallen as he admitted the level at Spurs is currently "not high", as he continues his revamp.
It might not be a passport trip but Celtic fans would savour a visit to the brilliant Tottenham Stadium. A tie of real gravitas.
Basel or Qarabag
A pair of former foes - Basel and Qarabag will face off on matchday six to see who wins Group H.
Both of them are on 11 points and Scott Brown will likely be called upon if it is the Azerbaijan side, after they wiped the floor with the Dons in qualifying.
Basel will hope a home win will see them through to the last 16 and avoid an extra round of European fixtures.
And a host of sides could do without a trip to Eurasia at a time when domestic football is being ramped up during a busy fixture period.
