Neil Lennon believes that Celtic's Emirates Cup showings can trigger one of the greatest ever European comebacks.
Overturning a three-goal deficit is the challenge tonight against Sporting Braga with the absence of Aiden McGeady another factor weighing against Lennon in his first home match in permanent charge.
Last week's 3-0 defeat in Portugal brought a halt to any pre-season optimism with Celtic looking like missing out on the Champions League for the second season running.
Facing Lyon and Arsenal on successive days on the back of the Braga defeat seemed like asking too much of the players but Lennon was heartened by the way that his side came back in both games from being 2-0 down to draw with Lyon and giving Arsenal a fright by fighting back to lose 3-2 after being three down five minutes into the second half.
"I am more confident now than I was before we went to London," Lennon (pictured below) claimed. "Attacking wise, some of the football in the last half hour against Arsenal was fantastic.
"I've spoken about bringing the thunder back to Celtic Park and that starts now. We have to be totally committed in this game and give everything.
"It won't be gung-ho because we must also be disciplined and concentrate. But it can be done and I've told the players that.
"We scored four times against Artmedia Bratislava in the second leg -- and it could easily have been five.
"We lost 3-0 to Benfica over in Portugal, but we beat them 3-0 at home. You draw on those experiences and you have to believe this tie is not over yet.
"We have to keep the door shut or we'll end up having to score five. Our concentration levels at the back have to be at the maximum. They are a very good counter-attacking team.
"So the worry is the other end of the park. It's a worry anyway, regardless of how well we go forward.
"If we lose an early goal it flattens everything. It's important we don't concede in the whole 90 minutes, really, but there's not a mad rush to score.
"I would like to start at a decent tempo and try to make them defend, try to see what they've got. We will have to take risks. But my back four are well aware of that."
The back four and goalkeeper Lucasz Zaluska are Lennon's big concerns tonight after conceding eight goals in three games against Braga, Lyon and Arsenal.
Lennon has gone on record as saying that he's looking to bring in another goalkeeper and left-back but admits that any more transfer activity is linked to the sale of McGeady.
A £10m fee from Spartak Moscow would allow the new Hoops boss to add to his squad with the club appearing to be anxious for McGeady to move on.
"What comes in goes back out on the football side," Lennon confirmed. "That's been made clear.
"I think we need a couple of areas to improve the squad. But I don't think it'll take all that money to do that. It's up to me whether I spend that amount or not.
"Aiden is in Moscow, that's as much as I know. He was a wee bit apprehensive but he's gone to have a look at the facilities and the stadium and see what Moscow can offer him.
"As far as I know he was travelling to speak to Moscow and have a look at the club and the surroundings and take things from there."
Daryl Murphy will be looking to make his home debut tonight but faces competition from Georgios Samaras and Gary Hooper for a striking slot.