"The first half was really good because we were in control, had plenty of possession but you must finish the game," said Benitez.
"I don't know why but we couldn't get the second goal. In the second half they were more physical and aggressive and when we conceded a goal we became a little bit nervous.
"Gerrard won the game for us at the end and we know how good he is at getting from box to box, but as I said we should have had the game won a lot earlier than what we did."
The Reds boss revealed that he will have to assess the fitness of Sami Hyypia at Melwood on Thursday to see whether he will be available for Sunday's trip to Manchester City.
"Sami had a problem with his ankle and we will need to see how it is. I will need to talk to the doctor," added Benitez.