There is no preamble to the Champions League.

Celtic's third qualifying round tie against HJK Helsinki can already be considered a pivotal moment in the club's season. It will concern Neil Lennon that his side has yet to play a competitive match, but that quirk of the Scottish football calendar will provide little comfort to supporters if his side fail to overcome the Finnish champions over two legs, beginning tomorrow night. The league season will already look mundane to the Celtic fans, with the absence of Old Firm fixtures, which places even greater significance on the Champions League.

The competition is treated as a welcome distraction in Scotland, since the Old Firm enter it with their hopes restricted to reaching the group stages. The elite of European football have successfully detached themselves from leagues outwith the top five, and clubs from the second tier of nations primarily treat it as a source of revenue. There is still some currency in the prestige of competing, and Celtic are attempting to tap into both.

HJK are midway through their league campaign and will arrive in Glasgow believing that there will be some competitive advantage in their conditioning. It is a hazard that the home side will be expecting, although Rangers could not overcome it at the same stage last season, against Malmo. To prepare for the tie, Celtic treated last Saturday's friendly against Internazionale as if it was a competitive game, and the display was promising, even if the Italian side are at an early stage of their pre-season campaign.

Lennon would mull over certain quibbles during the team's preparations, with only three goals and one win from six pre-season games, but a manager is naturally preoccupied by inconsistencies he would like to solve. The back-line, too, remains unsettled, but Lennon will trust that the players and the attitude that delivered the title for his side last season will be enough to meet the challenge of their Finnish opponents, even if HJK have long been established as the country's strongest and most successful team.

"They will be fit and they will definitely be up for it," said Thomas Rogne, Celtic's Norwegian defender. "This is also important for them and to play Celtic is big for their [players'] careers. We have prepared really well. The whole pre-season has been about this game. We have been treating the last few matches as proper tests and I think we are ready for it.

"The results haven't been the best, but the focus has been about getting fitness. We are ready now. Everyone wants to play in the Champions League. It's important for the club and for the fans. It's massive for us. It is the biggest thing you can achieve with the club."

Peace of mind is elusive when a knockout tie, even over two legs, carries such consequences. There is a financial windfall for making progress from this stage and then the final qualifying round, but these games will also set the tone for Celtic's season.

Lennon praised his players last Saturday, but his mind would already have been working through the permutations for his defence and attack. If Kris Commons, who has impressed during pre-season, and Anthony Stokes do not recover from ankle knocks, Lennon must choose between a two-pronged attack or playing Georgios Samaras up front on his own, a role that does not appear to suit the qualities of Gary Hooper.

The defence is more complicated, since there are several potential line-ups. It is most likely to be a combination of Adam Matthews, Rogne, Charlie Mulgrew and Emilio Izaguirre, but Lennon also experimented with Mikael Lustig at centre-back last Saturday, and Kelvin Wilson could also return to the side, despite suffering from poor form.

These are the kind of details that fill a manager's concentration, but Lennon will also expect the Celtic Park atmosphere to be an influence on the game. The directors will also be fretting over the crowd, since the friendly against Inter was not a sell-out and season tickets are still on sale – so the turnout for the Champions League tie will be an indicator of the mood of the Celtic fans, some of whom have been grumbling about season-ticket prices.

"We always want the crowd on our side and ever since I came to this club they have been brilliant," Rogne said. "Saturday was a friendly but Wednesday is serious business again and hopefully as many as possible will support us. I believe Celtic Park on a Champions League night is something different. The fans are very important to us as they give us a boost and give us confidence.

"They can also put off the opponents as they can get a bit scared. The reason people watch us is because they love Celtic and not because of anything else."

Wednesday's tie is a test of Celtic's readiness, on and off the pitch.