The home side took the lead through George Boateng's first goal of the season with 26 minutes gone, and the Reds boss responded by introducing Ryan Babel at the break.
However, the visitors had to survive a major scare when Stewart Downing, amid speculation that Tottenham are ready to push home their interest in him, rattled a shot against the post.
Benitez admitted he was disappointed not to have won the game as a late assault was repelled at full stretch by the Teessiders, for whom Schwarzer made fine late saves from Steven Gerrard and Sami Hyypia.
The gap to the top of the table remains at 12 points, but he knows time is starting to run out.
He said: "In this position, you cannot think about the leaders, you must think about the next game against Luton, and after the next one against Aston Villa.
"You can play well, you can create chances, but you need to win. You can talk and talk, but at the end of the day, you must win on the pitch.
"When you talk about a draw away, sometimes you think that is good, but especially when you are trying to reduce the gap and be closer, you must be disappointed."