Real Madrid goalkeeper Iker Casillas says Barcelona will struggle to match their clean sweep of 2009.

Casillas is convinced Barca will falter, particularly after seeing them held at home in the Liga and losing to Sevilla in the Copa del Rey this week.

"Barcelona's players are human and it is normal that they cannot keep up the same pace as before," said Casillas.

Asked who Real should sign to strengthen the team, the keeper smiled: "Who knows? Villa, Silva, Cesc ..."