Wednesday 6 April 2016 23:33, UK
Zinedine Zidane insists Real Madrid did not underestimate Wolfsburg, but lacked intensity in their 2-0 defeat in Germany.
Real now face an uphill task to qualify for the Champions League last four after the first-leg defeat, thanks to goals from Ricardo Rodriguez and Maximilian Arnold in the first half.
Zidane blamed the loss on their first-half showing, despite having chances to take the lead early on.
"I'm not happy, above all with the first-half. This can happen If you don't play with intensity from the start," said Zidane.
"It wasn't about a lack of confidence. We knew that we had a difficult game and we had one. We were not concentrated enough. We did it better in the second half but we did not score.
"That's football, that's how difficult it is. That's what happens when you don't play with intensity from the start."
Real have won the Champions League just once since 2002, and must produce an improved performance back at the Bernabeu on Tuesday to progress. Zidane says staying united is the way to achieve a last four place.
"Despite everything I'm proud of the team, we have to think about resting well and think about the return because we have the chance to change everything in the return leg," he added.
"We have 90 more minutes to try and achieve our objective. We need to be united and continue what we have been doing."
Wolfsburg, last season's Bundesliga runners-up who had scored only one goal in their last three matches, are competing in the last eight stage for the first time in their history, and showed more energy than their Spanish opponents on Wednesday.
"You have to bring that energy if you want to win," said Wolfsburg manager Dieter Hecking. "I was laughed at when I said yesterday that we may have a chance. Real had their opportunities early on and we were a bit lucky.
"We pulled together, we found the spaces and played very well. Now we will go to Madrid, knowing that we have a chance to advance."