كتب : Mohamed Sabe
"I said before that if we didn't perform we wouldn't win the game and we didn't perform," Beckham told a press conference after the game.
"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," he explained.
Real, who have not lost a league game since the beginning of the year, struggled to find their form against the Gunners in the first-leg of the UEFA Champions League round of 16.
Thierry Henry scored Arsenal's only goal two minutes after re-start to give the Premiership side a comfortable win ahead of the second-leg in London.
"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.
"From the first five minutes you could see we weren't playing with the confidence we've been showing. I knew Arsenal wouldn't come here and defend," he added.
The 30-year-old England captain, who was playing his first match against a Premiership side since joining Real in 2003, knows playing at Highbury will not be easy.
"It's going to be hard. I have played at Highbury a number of times and I know how difficult it is," he said.
"But it's possible - we've got the players. If we get one goal and then two, we're through, but we have made it very hard for ourselves."