Newcastle went 1-0 up through Isaac Hayden before Willy Boly equalised during a goalmouth scramble in the 95th minute.
Boly headed home from a looping cross after the ball seemed to slip through the hands of goalkeeper Martin Dubravka.
Benitez was quick to show his disappointment after the game, and criticised his goalkeeper for his lack of strength.
“You have to be disappointed, we knew it could be a difficult game,” Benitez said.
“You could see we had control and then we scored the goal, after that you could see a change but we still had some control.
“We had counter attacks where we were in good positions but we could’ve done better with the final pass.
“They were pushing but we should done better, these kind of crosses you can do better and punch the ball.
“It was not clear in the replay but we have to defend the cross better, you know you’ll be under pressure and you have to be strong enough.”
The late draw leaves Newcastle a single point above the relegation zone with 12 games left to play.
Newcastle goalscorer Hayden also spoke after the game and backed his teammate Dubravka to bounce back.
He said: ”He is a top class goalkeeper; we win as a team, lose as a team and draw as a team, so there will be no blame at his door.
“It’s difficult to put into words.
“I don’t know whether it’s a foul or not, it looked a foul from the bench.
“It’s just another bit of bad luck on our part. We deserved the three points but it wasn’t meant to be.
“We all have to take responsibility.
“Everyone has made mistakes throughout the season but we just have to stick together and get as many points as we can.”