Schalke has earned 13 points from its last five Bundesliga games to lift it to second place, nine points behind Bayern with seven games left.
"We're going to play our hearts out for 90 minutes - 120 minutes if necessary," said Schalke defender Heiko Westermann. "Then we'll see who goes through. If we start like we played in the second half of the first leg, we have a chance.
A 12th minute goal by 17-year-old Bojan Krkic made the difference in the first leg. Bojan was making his sixth Champions League appearance.
In addition to the young star, Barcelona's squad has a huge advantage over Schalke in the experience department. Its players have played in an average of 45 Champions League games compared to Schalke's 10.
Also, Barcelona players on average have 55 national team caps while Schalke's have an average of 17.
Schalke's leading scorer in league play, with nine goals, is German international Kevin Kuranyi.
Kuranyi, who has regained his national team spot after being dropped before the 2006 World Cup, is supported in the attack by fellow German Gerald Asamoah and Turkish international Halil Altintop.
Barcelona, although struggling in La Liga, is undefeated in its last 10 Champions League games. Barca will be without injured Ronaldinho and Lionel Messi, while Deco is doubtful.
Schalke's only European title is a 1997 UEFA Cup win and it has not won the German league since the creation of the Bundesliga in 1963.