Jokin Aperribay, president of the La Liga outfit, admitted that his side are hoping to sign the Belgian, but ultimately it's up to the English side to decide on his future.
The 22-year-old broke into United's first team during the 2013-14 season but hasn't been able to lock down regular minutes in the time since.
Loan spells with Borussia Dortmund and Sunderland followed, and it seems the man who found favor under David Moyes may be on his way out the door for good.
While Celtic has been mentioned as an option for the winger, Aperribay made it clear the Scotish club wasn't the only team with an interest in him.
"It's true that we are interested [in Januzaj] but we are not in talks with Manchester or with him," Aperribay said at a press conference as quoted by Mundo Deportivo. "We are waiting for the decision of Manchester United and then we will act. There are more teams interested in him and his signing won't be easy."
Spanish publication Marca reported that United were ready to let Januzaj leave for £8.8m. The 22-year-old failed to impress Jose Mourinho after his season-long loan spell at Sunderland.