The visitors took the lead via Djibril Cisse after a dominant first half display but we hit back after the break and equalised via Jermain Defoe's striker after 71 minutes.
Benitez said: "The first half was good. We had lots of opportunities and I was very happy.
"The second half was more difficult for us because they played more forward balls and we got tired. When teams play long balls it means you have to go backwards to recover possession and we got a bit tired doing that.
"That's why I took our two strikers off during the second half. I wanted us to press their defenders more and I thought Cisse and Baros were getting tired. They will maybe disagree, but my opinion was they were tired."
Liverpool boss Rafael Benitez declared himself happy with a point after our opening day draw at White Hart Lane.