Liverpool need victory to keep their European hopes alive and Benitez is concerned yesterday's defeat may unsettle his players.
He said: "We now have a difficult game against Lyon. My concern now is we have too many injuries and we have to analyse which players will be available for Wednesday.
"All the managers want to win games and when you are not winning you have to analyse why, and we are doing this.
"Everyone saw the game against United and you saw we have confidence and we can do it.
"It's a question of taking your chances when you create them and don't make massive mistakes like today and give a lift to the other team.
"We have to be calm, keep working hard and find solutions."