THE Champions League is all fun and games until someone loses a tie.

Neil Lennon cut a serious figure at Celtic's training ground yesterday and Georgios Samaras, who spent quarter-of-an-hour telling reporters how angry he was, was not a bag of laughs either. An air of tension hung over Lennoxtown and the strain will be even easier to detect when the masses gather this evening. The manager and his players have become seasoned European campaigners but being addicted to the Champions League heightens the fear of withdrawal.

At least £15m in income, the chance of another night like when Barcelona visited, the thrill of having a place at football's top table and competing with them as equals: it is all of that or nothing for Celtic tonight. Death or glory in August. The fact failure would result in them dropping into the Europa League groups stage is not exactly nothing, but it will feel like it to just about everyone inside Celtic Park if Shakhter Karagandy have prevailed at the end of this play-off second leg.

Celtic long to think of themselves as a Champions League club and that status is hanging by a thread. About the only good that came from last week's 2-0 defeat in Astana was that it made it easier to shift tickets for this fraught, unpredictable second leg. Celtic might run in three or four unanswered goals against this modest Kazakh team and all the anxiety and criticism will dissolve. Or maybe they won't. It's almost seven years since Celtic won a home Champions League game by three clear goals. Shakhter have been widely disparaged since the first leg but they are likely to be sceptical about Celtic's supposedly superior talents given that they scored twice against them and kept a clean sheet. Celtic might have known exactly how Shakhter would play last week - defensive, 4-5-1, direct and physical - but errors meant they still could not cope. Tonight there will be the constant fear that if Shakhter score once, Celtic need four. The tie is beautifully, grotesquely balanced.

It will be one of those odd nights when Celtic need thunder from the stands to unnerve inexperienced visitors, but must perform without feeling pressurised or rushed by the demands of a fretful support. Frustration and eventually panic will be transmitted the longer Celtic go without opening the scoring, or if they concede. Lennon will hammer home the message that they must play with controlled aggression and composure. A goal at any time in the first 60 or 70 minutes would still give them time to crank up the pressure in search of a second. None of it is likely to result in a soothing, straightforward night.

Lennon conceded that if his team pull this one off it would be as sweet as any victory he has known since becoming manager. "It would be, considering everything that has gone on over the last six or seven weeks," he said. "The amount of qualification games we have had and off the back of what happened last week as well. The squad is really stretched at the minute so we are trying to do the best patch-up job we possibly can. These things happen. I am not putting my excuses forward before the end. We are a bit stretched but I think we will prevail."

Being stretched was a reference to the sale of Victor Wanyama, Gary Hooper and Kelvin Wilson for around £20m, with the squad looking much lighter as a result. "I don't feel short-changed but I think the squad is short," Lennon added. Lassad, Miku, Thomas Rogne and Paddy McCourt have also left this summer with only Amido Balde, Virgil van Dijk, Steven Mouyokolo and Derk Boerrigter arriving. Yesterday they were linked with Lazio's 29-year-old French centre-back, Michael Ciani.

"Seven players have gone out the door, four have come in and out of those seven we lost three very important players," Lennon said. "We have tried to bring players in and that has not been forthcoming. I don't feel shortchanged, it's just the way the circumstances have thrown themselves at us. But we still have a game to retrieve it all. I'm not saying it's over. It's not. I think we are still very much in this tie.

"I think the players are still angry from last week. There is always a fall-out after these games and things get said, so they will be motivated to play and to prevail. The performance made them angry, the result made them angry, and things that have been said after the game. That's all the motivation they need. Since the final whistle over there they couldn't wait to play the return game.

"They have to keep their discipline but the team is very disciplined, especially in their tackling and in how they deal with the referee and stuff like that. People will maybe want us to be gung-ho at the start but there are 90 minutes to score two goals or possibly three. If we concede, we've just got to score four or five. They are well-versed in what they have to do. The fans will have to be patient, that goes without saying. We might not score until the 70th or 75th minute but that still gives us 15 minutes to get another one. It's a long time in football, that."

Shakhter plugged into a powerful atmosphere in Astana last week and there was a feeling they were being charged by the support of the whole of Kazakhstan, a country which has never had one of its clubs go this far in the competition. "Sometimes dealing with it for the first time means there is no fear or you have no worry about the consequences," said Lennon. "There is no real pressure on them and there hasn't been since this draw. But it's different when you are on the pitch and you are away from home and the opposition get a head of steam up. That's when you start to feel the pressure. If they think the job is already done that is a very dangerous thing, because it's not a massive deficit to overturn."

Parkhead had better ready itself. Celtic's whole season will be shaped tonight.