It was a game which, for long spells, looked to be heading for a draw, before Oscar came off the bench to make the difference.
Benitez said: "We started really well, in the first 20 minutes we were in control and we had some chances.
"After that they were pushing and we had some problems in defence. Individually the defenders were doing a great job, but as a team we had problems.
"We changed a few things in the second half and had more control, the concentration and intensity was much better. Eighteen attempts on goal away from home isn't bad but we must be more clinical in attack."