Rafael van der Vaart, who missed the 2-1 win at the Stadium of Light on Saturday with a calf injury, should be fit but Bale, despite recovering well from his back problem, is unlikely to make the trip.
Redknapp said: "Gareth is not too far away. He's not going to be fit, I don't think, for Tuesday, but he's not too bad."
He added: "The specialists have seen it, he's had an epidural injection. Peter Crouch has had the same problem and he is fine - in fact, his back looked a lot worse on the scan.
"He shouldn't be too long, but Tuesday may be just a bit too soon for him. But van der Vaart should be okay.
"You saw what Gareth did against Inter Milan, when he terrorised them, really, and that would be in their minds an awful lot, I'm sure, if you asked them.
"Everybody in Italy talks about Bale - I went over and watched a game and everyone was asking me: 'Is Bale fit? Is Bale fit?'.
"He would scare them to death, for sure."
Source: PA
Source: PA