More worryingly was the injury to striker Fernando Torres who limped off in the first half with a suspected hamstring strain.
"It could be he is out for seven to 10 days, but until he has the scan we won't know."
As to the game itself Benitez is aware his side need to improve.
"In the first-half both teams had more or less same opportunities and in the second half I thought we started well.
"In the last 15 minutes they were pushing quite a lot. It was a game that we could have won and so could they.
"It is not that we should have finished quicker. I think you have to give credit to the defenders.
"We were controlling and creating the opportunity for the final pass," Benitez told Sky Sports 1. "We have to improve the final pass and that could be the difference."