However, with City and United set to meet in the Manchester derby on Sunday, Benitez says it is too early to dismiss Chelsea's challenge.
Ahead of his side's trip to Sunderland on Saturday, Benitez said: "I'm not worried about the distance (in points). It's important we win so we are close, but all we can do is think about one game at a time.
"We have to improve the team and be mentally strong enough to compete in the second part of the league.
"At Valencia we were eight points (note: actually six points) behind in January (2002, before going on to win the Spanish league title).
"If we have to do the same here, we will do it. But we have to show the same character we have.
"The main thing is about the evolution of our team. If we're stronger, we'll be able to win games in a row. We have to find form."