Schalke centre-back Christoph Metzelder said on Monday that his side's shock elimination of Champions League holders Inter Milan was a watershed moment for the club.
Schalke will host Manchester United in the first leg of the semi-finals on Tuesday, having torn Inter's trophy defence to shreds with a wholly unexpected 7-3 aggregate victory in the previous round.
The Bundesliga outfit have never graced the last four of Europe's elite competition before, but Metzelder warned United not to take them lightly.
"We have to be realistic, we're not the favourites," said the former Real Madrid and Borussia Dortmund player.
"We're featherweights, clearly, but I think that after the San Siro (where Schalke beat Inter 5-2), Europe realised what we were capable of doing.
"By winning the second leg as well, we confirmed it. Man United might have been happy to face us, but we're here and we're going to give everything."
He added: "The whole of the footballing world will be watching Gelsenkirchen and we'll give the best of ourselves to continue on our path."
Schalke, currently 10th in the Bundesliga, cannot compete with United's experience on the European stage and Metzelder conceded they were following a steep learning curve.
"The team isn't used to playing more than one match per week, apart from Raul," said the 30-year-old Germany international.
"German teams have always struggled to string results together."
United, who won the last of their three Champions League titles in 2008 and lost to Barcelona in the 2009 final, have yet to concede a goal on their travels in Europe this season.
Sir Alex Ferguson's team have acquired a reputation for defensive miserliness in European competition and Metzelder warned Schalke's fans not to expect the kind of attacking onslaught they witnessed against Inter.
"They're a disciplined team, who don't leave a lot of space," he said.
"We're not going to score five goals at Man United."