Real Madrid goalkeeper Iker Casillas has admitted that his team were left frustrated by their inability to score in Tuesday's Champions League quarter-final first leg at Atletico Madrid.

Los Blancos had a number of chances in the first period, but were denied on six occasions by Atletico goalkeeper Jan Oblak.

Casillas, however, has conceded that Atletico improved in the second half and restricted the visitors to few opportunities.

"The first half bore no relation to the second. Real Madrid deserved much more from the first half, but we were up against a fantastic Oblak. After the break Atletico calmed things down, prevented us from attacking on goal and controlled that aspect of play," Casillas told Real Madrid's official website.

"The tie is wide open. A 0-0 result ensures for a great second leg and I think both teams still have a chance of going through. We're hoping the fact that we're at home will mean we put in a good performance, feed off the fans' energy and get through the tie, which we knew from the beginning wouldn't be easy."

Real Madrid have not beaten Atletico in six games across four separate competitions this season.