"Pep is the secret weapon of this group," Valdes said in an interview with Spanish publication Sport.

"Leaving aside the sheer quality of players, he is a very special talent, along with the rest of his coaching staff.

"Pep Guardiola is one of the best secrets and the most important member of the team."

Guardiola was appointed as Barcelona coach in 2008 following the departure of Frank Rijkaard.

He led the Catalan giants to a host of titles, including two successive Primera Liga triumphs and one European Champions League accolade.