Fear is not acceptable, says Keller
Schalke's hopes of reaching the quarter-finals were effectively ended in Gelsenkirchen three weeks ago as Real romped to a 6-1 triumph.
There would appear to be little more than pride for Schalke to gain when the two teams meet again at the Bernabeu on Tuesday.
However, after seeing Bundesliga rivals Bayer Leverkusen respond well to a first-leg thrashing against Paris Saint-Germain with an improved performance at the second time of asking, Keller is hoping to keep Real in check.
"Bayer Leverkusen played bravely against PSG in Paris (losing 2-1 after a 4-0 defeat on home soil) and we want to do the same," said Keller on Monday.
"We must be realistic; Real Madrid are an amazing team and when you lose 6-1 in the first leg it is not easy to reach the quarter-finals. Real Madrid and Bayern Munich are the strongest teams in the world.
"We have a young team and this match can be a good experience process. We have to do better than in the home match.
"We must be more compact and not let the opponent grow. Fear is not an acceptable word in football. We are going to try to do our best."
Schalke are currently third in the Bundesliga and seeking to secure qualification for next season's Champions League.
Keller is aware a positive result against Real could provide a welcome boost ahead of the team's domestic run-in.
"We want to perform well against Real Madrid. Do that and we will gain confidence for the final Bundesliga games," he added.
Midfielder Roman Neustadter is hopeful he and his team-mates can enjoy the experience of playing in the Bernabeu.
"We had a bad result in the home match but to play here is a great experience for every player," said the 26-year-old.
"This is a step in a young player's evolution. We will try to get a better result. We are professionals and we learned from the home match.
"I do not know if we are going to win but we will play with intensity and enjoy the atmosphere. Each football player knows about Real Madrid. We know how they play and we will try to do our best."