"The team is playing well but sometimes you can see some players really tire," said Benitez.
"On Saturday Steven Gerrard, after the stomach problems he had, was a little bit tired at the end, and Torres could be more or less the same.
"Sometimes you don't know. Players like Sami Hyypia can be fit in two or three days but maybe they need more. We will check during the week.
"Sami had some problem in his hamstring the other day but we had to protect him and at 34 it's very difficult. We need to think about who will play in these positions. If we need to change players it's not a problem, because you can see the level of Lucas or Xabi Alonso. We can use players with enough quality."