That's when Ronny Deila will discover the opposition for his first competitive game in charge of Celtic.
A month today, the ties will kick off, and a new era for the Parkhead club will begin -hopefully with a victory.
But should the Hoops fans already be worried?
Even before the new manager gets the chance to meet the players he has inherited from Neil Lennon, some big holes are appearing in the fabric of the team Deila will be able to pick for these crunch Champions League qualifiers.
The Bhoys in Brazil - Efe Ambrose, Fraser Forster and Emilio Izaguirre - are likely to be excused boots for the first few weeks of the campaign to give them time to recharge their batteries following a prolonged season for the trio which is still running.
There is also the not so insignificant matter of question marks hanging over the fitness and preparedness of players who finished last term nursing serious injuries.
Nir Biton suffered a groin problem while playing for Israel in March, and was unable to kick another ball for Celtic in 2013-14.
Jame Forrest's stop-start campaign also fell victim to damage sustained while on international duty. The groin problem he flared up while training with Scotland ahead of their in friendly in Poland eventually forced him back into the operating theatre for more surgery.
Adam Mathews was another key component of Lennon's side who failed to see out the season, his recurring hamstring injury ruling him out of the run in and Wales' end-of-season friendlies.
Tom Rogic joins them in the band of men who have work to do to ensure they are fit and ready to go under the new boss.
The midfielder went back to Australia to get the game time he need to secure his place in the Oz squad at the World Cup Finals.
But the pelvic problem which has blighted his career since he moved to Celtic flared up again, not only causing him to miss the final cut for the 23-man squad taken to Brazil, but raising also the spectre of surgery to get to the root of the inhibiting injury.
While all of the above will eventually be available to Deila, could the biggest loss of all be a man who has been pivotal to Celtic's success in Europe for the past few years, but who has now taken his final bow in the Hoops?
Watching Georgios Samaras play for Greece in Brazil is a reminder of what he can bring to the party, and what Celtic will now be missing after the club failed to renew his contract.
His languid style may have infuriated as often as he inspired during his six years at Parkhead, but what can not be argued is that Sami's absence has created a huge void in the team, one which Deila must address immediately.
The goals record the Greek enigma could boast - nine in the last two seasons - underlines how vital he was to the team's success rate, especially on the road.
Not just in qualifiers, though, at one stage in 2012-13 he became prolific, finding the net in five consecutive away games in Europe.
Samaras did not only score in qualifiers in Helsinki and Helsingborgs, he also did it on some of the biggest stages against some of the biggest opponents, including Barcelona in the Nou Camp, Spartak Moscow in the Luzhniki Stadium, and Benfica in the Stadium of Light.
That's huge boots for anyone to fill. As a relative rookie in European competitions, Deila will lean heavily on the experience gained by the likes of Scott Brown, Charlie Mulgrew, Emilio Izaguirre and Commons.
How reassuring it would have been to have been able to add Sami's qualities, and goals - he was top European scorer again last term with four - to that assets column.
So who will be given the call to take over? Commons scored for fun domestically last term, but his strike rate was nothing like as prolific on the European stage, two in 11 appearances.
His most important goal was the opener in the second leg of the play off against Shakhter Karagandy. Likewise, Forrest was a very important player that night, scoring the goal which took the Hoops through to the group stage 3-2 on aggregate.
He finished one behind Samaras, who had knocked in the second goal against Shakhter, in the top scorer stakes in Europe.
But given his track record for being forced to sit out long periods, can he be relied upon to be Deila's go-to man?
Anthony Stokes has the durability Forrest lacks. But, like Commons, he has been more effective setting up chances for others - it was his clever play which made the opening for Forrest against Karagandy - than banging them in himself. In fact, he didn't score a single goal in 11 outings in Europe last term.
Leigh Griffiths? Having arrived in January, he is, as yet, untested at that level.
So, with Sami gone, Deila and the Hoops fans are holding out for a new European hero.
The auditions will begin when the bulk of the squad report back for pre-season training a week tomorrow and will continue at the training camp in Austria and through the series of warm-up matches played there.