The Magpies blew a golden chance to take all three points when Kenedy was presented with a stoppage time penalty.
But his weak kick was easily saved by Neil Etheridge and United had to settle for a point.
Benitez said: “It was a strange game. We knew it would be physical and difficult, and it was.
“We put ourselves under pressure with some mistakes.
“After there were many things I did not like too much but the positive was we got a point, and with the team-mate and effort.
“The three points were there for us, so I'm disappointed."
And when assessing Cardiff City during the 90 minutes, Benitez said: “They were dangerous because they have big lads, but we were doing OK.
“We missed the final pass on counter attacks, and we needed to take our first-half chances.
“We missed a bit of control, and then we missed the penalty which was the key."