The Argentine midfielder did not fly out to Florence for the Group E match after pulling a hamstring in training, which means Steven Gerrard may be used in a less advanced position to cover.
"It's not a problem. We can manage with Stevie or another player," Benitez told a news conference, adding that Mascherano should only be out for a few days.
"It's not good to lose a player like Javier but we'll try to find a solution. There are three or four others who can play there."
Fellow midfielder Yossi Benayoun should be fit, Benitez said, after reports that the Israeli had suffered a leg injury during Liverpool's 6-1 demolition of Hull City on Saturday.
"It's a question of little things that we can fix, if we keep working together," he said.
"It's a question of time to find the right balance. Sometimes when you're attacking a lot you have more problems in defence."
"That was a great night in the San Siro, I enjoyed every minute of it and hopefully we can do the same against Fiorentina," he told Liverpool's website.
"It will be great if we can win in Florence and get six points from the first two games. It would give us more confidence ahead of the other group games."
"You stop him with good organisation, tactical order and lots of fortune," said Prandelli. "He's an extraordinary player. You have to hope you don't meet him on a good night."
"The word Heysel implies particular things that have nothing to do with Liverpool or the game of football," Prandelli said.
"Meeting Liverpool again does not take me back to that dramatic experience. Now I want to transmit the joy of playing against a great team like Liverpool."
