Ronaldo struck in the 2-1 setback.
He said: "There is no great drama because there are lot of matches left and we are well positioned. We knew that it would be a difficult match against a good team that are very strong at home. That's football and when you play against a great team the chances of winning are the same for each side.
"We must keep fighting, we have some home matches left and we must win them and get through to the next round. The only response that we can have is to play well and win the upcoming matches."