Commons' revelation confirmed the impression formed during Celtic's mediocre league performances so far. They have won only one of their last four league games, compared to four wins out in four European ties.
"From the first day of pre-season it has all been about qualifying for the Champions League," conceded Commons, one of the few players Neil Lennon exonerated from blame after Celtic lost to St Johnstone on Saturday. "There has been an extra buzz around the place for the last few weeks. As soon as the draw was made my phone has been ringing off the hook for tickets for one certain game [against Barcelona].
"There has been complacency in places in the SPL and our minds have not been fully focused, as has been evident in some of our results. If complacency has come in it is now time to concentrate on the Champions League."
Celtic's attitude and focus would be unrecognisable tonight compared to Perth at the weekend, he said. "I think as soon as we put the Champions League kit on, with the different badge, and we listen to the theme music then we will be fine. This is the stuff you ran out in your back garden and practised when you were a kid. I think the adrenalin and the excitement will get you where you need to be."
Commons, 29, will make his Champions League group-stage debut after 11 years with Stoke City, Nottingham Forest and Derby County during which he had not considered playing elite European ties. "I didn't think I would ever play at this level but it is not really the thing you think about at Stoke and Derby. As soon as I heard Celtic were interested in me, Champions League football was one of my aims.
"Growing up in the Nottingham area and playing for Forest it was a massive deal for that club to win the European Cup twice on the spin. Their stadium is littered with European Cup photos, the whole place is decorated in the history of this competition. I know exactly what it means to the people and the fans and I know how much of an impact the Lisbon Lions have on Celtic even to this day."
The aim for the current Celtic players was merely Champions League respect and credibility, he said. "I wouldn't say we want to become a force to be reckoned with but we do want to show we are no mugs. We want teams to think that they will be in for a tough game when they come to Celtic Park, and that they will have to work extremely hard to beat us even on their own patch.
"I hope everyone will take the game by the scruff of the neck and realise this is what they want to do. They have to take the occasion and think: 'I am a Champions League player and this is where I belong'."