But now Hoops' vice-captain Charlie Mulgrew can see a clear path to facing NK Maribor in next week's play-off, and can almost hear the famous Champions League theme tune booming out over Celtic Park when the return leg takes place a week later.
As much as the experienced player tries to play it down, the strain of the past few days as Uefa have dealt with the case against Legia Warsaw is clear.
Mulgrew did not even have the distraction of playing in Wednesday's SPFL opener at Perth, as he was suspended.
But he was delighted his team-mates were able to focus and get the win they needed to restore confidence after the heavy defeats to Legia.
"You have to shut all that out," he explained.
"You've got no choice, really.
"When that whistle goes, there's no hiding place and you just need to get on with it and get the result.
"We can't affect what happens, we can't change anything.
"So we've just got to block it out and get on with what we're doing."
The relief is tangible, however, and now Mulgrew wants to make amends when they play NK Maribor in the play-off.
He knows outsiders will deem Celtic lucky to get this second chance.
But he insisted: "None of this is our fault.
"We know we can play a lot better than we did in those qualifiers and Legia were a decent side.
"But what's happened since isn't down to us.
"The fixture [against Maribor] is there, so we can't go out feeling sorry for ourselves or embarrassed feeling we shouldn't be there.
"The fans will expect us to put on better performances, and we'll expect that from ourselves as well.
"So we just need to get up and get on with it, do our best and, hopefully, be involved in the Champions League.
"There's a long way to go, though.
"We've still got to qualify by beating Maribor, and that will be difficult."
The degree of difficulty is reduced somewhat by the fact that the second leg of this tie will be played at Celtic Park.
Being at Murrayfield was not the reason Celtic lost to Legia, but coming home is a big incentive.
"Playing in your natural surroundings and your home pitch has to help," said the Scotland star.
"The staff at Murryafield were brilliant and the pitch was great, but there's nothing like playing at Celtic Park."
Which is what they will be doing tomorrow for the first time since mid-May.
Mulgrew is sure that, even with the trip to Slovenia coming up fast, the Hoops will all be concentrating on adding another three points to their tally when Dundee United come to Parkhead for flag-unfurling day.
He said: "United are a good side. They like to play football and played well against us last season at Celtic Park.
"They've started the season well with two wins, so they're going to be difficult."