Aberdeen manager Derek McInnes hopes Dons fans can help overturn a 2-0 deficit in the Europa League third qualifying round tie with Real Sociedad.
The Pittodrie club announced all home tickets were sold out 48 hours before the clash with the La Liga side.
"If we can get the crowd into it, you just never know," he said.
"I always think at 2-0 at half-time the next goal is all important.
"We realise the importance of the away goal. We obviously never got one, and if Real get that goal it puts them in such a strong position.
"We're not thinking about that, we've just got to try and impose ourselves on the game, try and get on the front foot and cause them problems and if we can get that all-important first goal I believe we've got a fantastic chance of getting the next one.
"With it being a sell-out, we have to give the fans something to shout about.
"They are a very good side both on and off the ball, nothing that you wouldn't expect from a top Spanish side, and we'll have to be at the top of our game.
"It's an exciting game for all the players to be involved in. None of the players will be fazed by it, I'd like to think they'll be inspired by the crowd and the occasion.
"We understand we're not going to get it all our own way, there'll be spells when they'll really ask questions of us."
Last week, Aberdeen held on for nearly an hour in San Sebastian before finally succumbing to goals from David Zurutuza and Sergio Canales.
"We're huge underdogs for it, but we were underdogs before the first game," said McInnes. "It's an even tougher task but we'll go into it believing we can get a positive result.
"A 2-0 score-line wasn't any disgrace over there, but I still feel we can do better and we're hoping to show that improvement tomorrow night."