Real Madrid fullback Alvaro Arbeloa says Xavi was the difference in last night's 2-0 defeat to Barcelona.
Lionel Messi and Pedro grabbed the goals for the visitors.
But Arbeloa said: "There was a nerves problem. Barcelona were luckier than us and won the game."
"We cannot drop our heads and must go out and win every game."
"The key to the game is that we let five seconds loose to Xavi and he has made two passes that have served for Barcelona to win the game."
He added: "It is possible that Barcelona could lose, but we need to focus on winning our games. There are seven games and I hope we will give our best."