The Netherlands international believes Real Madrid boast "the best players" and are the most dangerous opponents left in the Champions League
The reigning European champions have been odds-on to become the first team to defend the trophy in the modern era throughout the tournament so far, but Robben believes such expectation counts for nothing against a side he believes are the most dangerous in the competition.
"They have the best players," Robben told Kicker. "If you have a 10 minute period where you switch off, you can suddenly concede three goals. There'll be a lot demanded of us.
"We are no longer favourites. Of course we want to win the Champions League again, but we're in the semi final – and anything can happen.
"Real are the most dangerous opponent we could have faced."
Wednesday's match at Santiago Bernabeu kicks off at 20:45CET.