"The three players had some problems," said Benitez.
"Keane and Gerrard and Alonso were tired, so we were trying to use players with fresh legs. We were trying to protect all of them by substituting them.
"I don't think they are serious. We will have to wait and see tomorrow.
"It was a little bit of a muscle problem for Robbie. Gerrard is okay. He was really tired and Alonso has a knock on his knee.
"We need to check with Keane. He will see the doctor."