Torres limped out of the first leg, won 1-0 by Liverpool, with an ankle injury and Spanish compatriot Arbeloa has not played since the match in Madrid because of a hamstring injury.
"Fernando is improving but it's still too soon to say if he'll be fit," Benitez told the club's website.
"He is working hard with the physios and we now have two or three more training sessions before we have to make a decision.
"I think he can be close but each player is different. We just have to wait and see. Arbeloa is much the same as Torres and we will try to push him harder over the next couple of days."
Another player hoping to return in Tuesday's home game is defender Daniel Agger, who has had a back problem.
Benitez added: "It will be harder for Agger but he too is working hard with the physios. All three could be close."
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