The players agent, Willie McKay, confirmed to skysports.com that the player was set to begin training with Rovers.
"Adrian is in England at the minute and he watched the Blackburn game at Manchester United on Saturday," he said.
"He will train with the club so that they can assess his fitness and I am confident a deal will be done.
"He has had chances to go to other clubs after leaving Alaves, but he feels ready to test himself in England. He is a proven player with a great pedigree having played with Valencia and Galatasaray."