Arjen Robben has stressed that Bayern Munich will have to be at their very best if they are to eliminate Real Madrid in the semi-finals of the Champions League.Both sides meet at the Allianz Arena on Tuesday and Robben expects a difficult encounter as he feels Los Blancos have 'incredible quality' in attack."We will give everything. You will see a great Bayern, I'm sure. We have no doubt that to eliminate Madrid, we will have to be at 120 per cent, at our maximum, and play the perfect game," Robben said to Marca."There are no secrets to Madrid. Their enormous potential is clear, but the most important things is that they have the best coach, who always knows how to play these games."They have incredible quality in attack. You can't give them a metre [of space]. You have to watch them closely the whole time."Robben wore the Madrid jersey from 2007 until 2009 before joining Bayern, but the Dutchman is no longer thinking about his spell at the Santiago Bernabeu."I had some very good years at Madrid. It's a great club, and it's obviously special to face my old team-mates, but I have been at Bayern for a while now and I am happy here. I am thinking above all about getting to the final, whoever the rival is."