Real Madrid midfielder David Beckham was dismayed by his team's lacklustre performance in their 1-0 Champions league defeat by Arsenal on Tuesday.
It was the first time the England captain has faced Premier League opposition since moving to Spain in 2003.
"I said before that if we didn't perform we wouldn't win the game and we didn't perform," he told reporters.
"Arsenal played well but we didn't play like we have done for the last two months. I don't know what happened. They got the space to enjoy themselves and they did well.
"Tonight was a really bad performance from the whole team. The players were not working for each other and were not getting in the box."
Arsenal threw off their poor domestic form as they made an electric start at the Bernabeu, slicing through the Real defence on several occasions in the opening minutes.
They secured a deserved win when French striker Thierry Henry weaved his magic to get way past three Real challenges before firing past Ilker Casillas two minutes after halftime.
"From the first five minutes you could see we weren't playing with the confidence we've been showing," said Beckham. "I knew Arsenal wouldn't come here and defend.
"I can't put my finger on it. We've got to stay upbeat but it's hard. To perform like that is disappointing. It's difficult now, but we have the players to go there and win".
The second leg of the first knockout round tie is at Highbury on March 8.