Real Madrid goalkeeper Keylor Navas has taken full responsibility for Borussia Dortmund's first goal in Tuesday's Champions League Group F clash between the two European giants.

Los Blancos appeared to be heading for a half-time lead after Cristiano Ronaldo had opened the scoring in the 17th minute, but Dortmund were level late in the first period through Pierre-Emerick Aubameyang.

It was a mistake from Navas that presented the Gabon international with the chance to level, however, as the Costa Rican punched a Raphael Guerreiro free kick straight into the box, and the ball hit Raphael Varane before Aubameyang fired over the line from close range.

Navas, who was making his first appearance of the season, has claimed that the free kick 'caught him by surprise', but has taken the responsibility for Dortmund's opening goal in what was a 2-2 draw on the night.

"The team put in a great effort. It is evident in the first goal I made a mistake. It took me a bit by surprise, I took the wrong decision and it cost us a goal. We will work on those details so it doesn't happen again," Navas told UEFA.com.

"I felt calm during the whole game despite the long months I've been out. Thanks to god I am back and able to help my teammates. My mentality doesn't change. I have to train hard, improve and it is the coach's decision [who plays]. I am happy to play because that is what every footballer wants. We would have loved to win but a draw is not a bad result."

Navas missed the start of the new campaign after undergoing surgery on his damaged Achilles.