Last week it was AC Milan in the San Siro, a week on Tuesday it will be Barcelona back at Celtic Park looking to avenge the bloody nose dished out to them last season.
Between now and the final group game on December 11 - in the Camp Nou, no less - it will practically dominate the conversations, thoughts and daydreams of every Celtic fan. In the absence of anything resembling a meaningful challenge - although Inverness Caledonian Thistle and their supporters may beg to differ - to their supremacy in the SPFL Premiership, the Champions League is the only show in town.
Not for Neil Lennon and his players, of course, who do not have the luxury of simply putting their feet up for the next nine days to prepare for the visit of Messi, Neymar, Iniesta et al. Not when there are domestic chores to attend to. Next on the agenda is Morton at home on Tuesday in Celtic's first involvement in the League Cup this season. It is perhaps the least of Lennon's priorities in the campaign ahead, but it is a tournament in which he clearly feels he still has something to prove.
Only in the League Cup did Celtic falter last season, the semi-final defeat by eventual winners St Mirren denying Lennon and his players a shot at claiming the club's first domestic treble in 12 years. As a manager he is yet to lift the trophy he won as a Celtic player in 2001 and 2006, and there is a determination in his voice when he speaks about Tuesday's game that suggests he has no intention of treating the threat of Morton lightly. In that part of the season when Celtic try to keep all their plates spinning, it takes an adjustment on the part of the players to go from the highs of the San Siro to a probably half-full, at best, Celtic Park against second-tier opposition, then travel to Kilmarnock, before welcoming Barcelona to Glasgow.
"As a player you get used to it and we had the same thing last year," said Lennon. "You might be playing Spartak Moscow and then Arbroath in the cup. [The League Cup] is part of our domestic treble and it's a trophy I have never won as a manager and Morton will come to play and compete. It will be a huge game for them and they deserve respect. I don't want to get all the plaudits [for playing well against Milan] and then lose to Morton. I want to keep going this little bit of momentum that we are starting to build."
The semi-final loss to St Mirren still serves as a source of regret. "Yeah. Even though we had chances in the semi-final, we didn't play anywhere near as well we could. Credit goes to St Mirren as well for that and you can get caught on the day. Again, we have to look at that and make sure we avoid that this year," the Celtic manager said.
A sense of what might have been also still lingers following Celtic's retreat from the San Siro. Having matched Milan for large swathes of the contest, a combination of wasteful finishing and some late defensive slips denied Lennon and his players the chance to put down an early marker in an undoubtedly difficult Champions League group. Watching the second half of the game on the aeroplane back to Glasgow confirmed the manager's initial instinct that his team deserved better.
"The first 25 minutes of the second half was superb in terms of the way we played and the chances we created," he added. "It's just disappointing because we gave so much to the game and we looked a Champions League team, if you want to describe us as that. I had confidence in the team going into the game and they reinforced that with the way they were playing on the night. To have a real dominant spell like that, particularly away from home, was impressive. We played bravely, we didn't sit or hold on for anything. We matched them in more or less every department. And that says a lot about the way they've developed."
Lennon, though, took little comfort from a strong performance that yielded no points. "I don't want this team to be gallant losers who get plaudits for losing. I want them to win and get what they deserve out of games. There are going to be times, like Barca here last season, when you probably don't deserve to win the game and you win it. I said that after the game - if you're looking at the stats and all that sort of rubbish, we got a lot of luck on the night. But we didn't get the luck on the night last Wednesday. As a manager you have to look at the overall performance. Can we replicate that in future games? I'm hoping that we can."
Defeat in the first group game would usually place greater pressure on a team to win their next match at home. When it is Barcelona who are the visitors, however, then usual logic is suspended. Anyone who felt the Catalan club were a diminished force following the 7-0 aggregate defeat by Bayern Munich last season were soon revising their opinion after Barcelona opened their campaign with a 4-0 walloping of Ajax.
"We've got Barcelona coming up who are playing very well by the sound of things," said Lennon with more than a hint of understatement. "To beat Ajax 4-0 is no mean feat. So there's a lot of pressure and a lot more riding on this game. I don't think you can really set your stall out to take points against Barcelona, but you can come up with some sort of plan to play against them and see where it takes you.
"They have conceded some goals in the league this year but they are winning games and scoring a lot of goals as Barcelona tend to, particularly at the start of the season. They will be hurting after last year with the way they went out - they looked more or less dead on their feet. But this is Barcelona we are talking about. For me, they have been the best club side in the last 25 years. That team from 2007 onwards, and any time with Messi in it, is going to carry some threat. We will change the way we played the other night. We won't have anywhere near the same amount of possession. You just have to accept that and make the most of what you have."
Emilio Izaguirre was not bowed by the challenge either. "It is our second [successive] season in the Champions League and I think we can do everything we need to get nine points from our home games, and see what we can do away from home," said the Honduran left-back.