Schalke 04 boss Jens Keller has conceded that his side will have to be at their best to overcome Real Madrid in the last-16 stage of the Champions League.
The German outfit welcome Los Blancos for the first leg on Wednesday with Carlo Ancelotti's side unbeaten in all competitions since the end of October.
"Behind Bayern Munich, Real Madrid is maybe the second-best team in the world at this moment. They have extraordinary players in each position and that is why it will not be an easy game for us," he told reporters at a press conference.
"We'll have to be compact at the back to achieve what might be a minor miracle of getting a result. But we are the home team and want to play in a brave way without hiding from Real.
"To be successful everybody has to play at 100%. Then it might be possible to achieve a little wonder."
Madrid were knocked out in the semi-finals by Schalke's league rivals Borussia Dortmund last season.
