Mata is also a top target for Arsenal.
"The chairman has been dealing with it," said Redknapp after Spurs' pre-season friendly win at Brighton on Saturday.
"He is a player we like, obviously, so do Arsenal, so do a few other clubs, but where it's all at I don't know.
"He's a player I went and saw when England played Spain Under -21s and I thought he looked fantastic.
"Whether anything happens I wouldn't be sure, the chairman is the only person who has been dealing with those transfers."