The Spaniard has been snapped up by Sam Allardyce as a free agent after he was released by Real Madrid in the summer.
After moving to Real from Celta Vigo, he helped Real to four league titles, three Spanish Super Cups, two UEFA Champions League crowns, the Uefa Cup and the Intercontinental Cup.
He has also been capped 53 times by his country.
Blackburn are waiting on international clearance before finalising his move to England.