Despite being only 40 miles from home, the Hoops had been a million miles off what was expected of them against Legia Warsaw as they withered under the pressure after a 4-1 first-leg defeat in Poland in their third round qualifier.
The 2-0 defeat in Edinburgh appeared to signal not just the end of Celtic's Champions League hopes but the start of a season without the carrot of top-level European football to keep players and fans in place while also attracting new ones.
But one Polish administrative cock-up later and, well, the rest is history.
Celtic's performance against Maribor on Wednesday was poles apart - pardon the pun - from those in Warsaw and Edinburgh as Callum McGregor's goal ensured they returned to Scotland with the upper hand.
However, the young Scot's goal may not be the biggest advantage for Ronny Deila's team when the Slovenians face the SPFL Premiership champs on Tuesday night.
It is the atmosphere inside the legendary stadium that Tom Boyd reckons will give Maribor the biggest scare as the Hoops take to the Parkhead turf for the first time in Europe this season.
Much better teams than the Slovenians have crumbled under the glow of the Celtic Park floodlights, with Barcelona among the European giants to be left in the dark there.
Former Celtic and Scotland captain Boyd admits the Hoops cannot underestimate how important the white heat of Paradise can be compared to the chill felt in Murrayfield little over two weeks ago.
He said: "Having to play away from their home pitch because it was being used for the Commonwealth Games opening ceremony certainly put things back for Celtic.
"It's a massive boost that they're now back at Parkhead. As good as Murrayfield is, it's not Paradise. It can't generate the same atmosphere.
"There's simply nothing to beat Celtic Park. It has the best atmosphere in the world.
"Visiting teams who have experienced a European night here have been quoted so many times down the years saying the same thing.
"It'll be a massive advantage for the team to have a packed Parkhead crowd behind them.
"European nights there are special, some of the best I've experienced since I retired."
THE result in Slovenia has already gone a long way to ensuring those special nights return this season.
Following their collapse in Warsaw in the previous round after going a goal up, Celtic looked assured on the ball against Maribor and confident in what they were trying to do.
However, no one at the club is naive enough to believe that the job is already done as the Premiership champs defend their vital away goal.
At the same stage in 2001, Celtic returned from Amsterdam with a 3-1 lead, only to endure a nerve-shredding night at Parkhead and a 1-0 loss to the Dutch giants before going through 3-2 on aggregate.
Boyd played in both games, and insists overcoming nerves and keeping a cool head will be as much the key for this Hoops squad as it was for Martin O'Neill's men 13 years ago.
"I remember when we played Ajax over in Amsterdam in the Champions League play-offs and beat them 3-1," said the former Celtic defender.
"Then we got them back to Glasgow and lost the game 1-0. It was very shaky early on but we managed to go through.
"Ajax had been behind us in terms of preparation. They had not started their league season while we had a couple of games under our belt. That can be so pivotal at this stage.
"There is a huge significance put on these European games because of the need to qualify for the Champions League. The money that comes with it is of massive importance to the club and Scottish football."
BOYD warned the Celtic players they will need to conquer the nervous tension that will inevitably accompany Tuesday's winner-takes-all encounter.
"Sometimes you just have to make sure the occasion doesn't overtake the game," he said.
"Because of what happened against Legia, there will be nerves when the players take to the field to play Maribor. But once the players take to the park they will just want to do well - for themselves, their team, the supporters and the club.
"There will be a determination to put things right in front of their own fans."
That is something Boyd is confident will happen if Celtic's performance in Slovenia this week is anything to go by.
With Maribor sitting back, the Hoops controlled large parts of the game and created enough chances to win the match.
That attacking promise is something Boyd is hoping to see more of on Tuesday night.
He said: "The performance in the first leg was encouraging. So was the display against Dundee United last Saturday.
"I was really surprised with how defensive Maribor were, especially in the first half. If you look at Celtic's frailties, most of them are at the back.
"But I thought Ronny Deila's side were well in charge of the game and should have come out with the win.
"It has been a mixed start for the Bhoys in Europe. They were good against Reykjavik then very poor against Legia. But they've been given a reprieve.
"That was a massive relief to everyone at the club, especially the players, because it gives them the opportunity to right a few wrongs.
"The level of performance in the last round just wasn't good enough but they restored some pride on Wednesday.
"That now bodes well for the second leg at Celtic Park where we'll have our usual wonderful European atmosphere."
Welcome to Paradise, Bhoys.