Sivero won the U21 Euros this summer with Spain.
And his campaign he has caught the eye of Real scouts as they consider a move for the youngster.
"I have a contract in Alavés and I am very happy," he said.
Sivera was grateful to Spain U21 coach Luis de la Fuente for backing him despite barely appearing for Alaves last season.
"The goalkeepers know that our position is very complicated, but I was lucky because the coach trusted me."