"He is improving. He is training, sometimes with pain, but with less pain every time," Benitez told a news conference on Tuesday.
"Clearly, he is not 100 percent fit and we have to wait to see how he feels."
Torres sustained an adductor muscle injury on international duty last month. He was replaced after 63 minutes despite scoring in Saturday's 3-1 Premier League defeat at Fulham.
Benitez said his team would face a difficult task with "11 to 14 members of the squad injured" including captain Steven Gerrard, Albert Riera, Martin Kelly and Martin Skrtel.
"We have a lot of problems but we still have good players, we still have a good team," he said.
"It's a Champions League game and a very important one. All the players available are ready to play. You can see the team spirit and the mentality of the players are very good. They are all professional players and they want to win."
Liverpool have lost six of their last seven matches in all competitions, including the 2-1 home defeat by Lyon two weeks ago, and their hopes of reaching the knockout stage will be hanging by a thread if they lose at Stade Gerland.
Lyon top Group E with nine points from their three matches and will qualify for the last 16 if they win.
Fiorentina, who entertain Debrecen, are second with six points, followed by Liverpool (three), and the Hungarians (zero).
(Editing by Sonia Oxley)