The scintillating form of leaders Juventus has left third-placed Napoli trailing the defending champions by 13 points in the Italian top flight.
With 15 games remaining, Benitez feels the gap is too wide to bridge, but is still hopeful of catching second-placed Roma, who have a four-point advantage and a game in hand.
"I don't think we can win the title now," Benitez told Onda Cero.
"But there is still a lot we can do. There is much we can improve upon.
"Our goal now is to get closer to (second-placed) Roma."
The two sides went head-to-head in the semi-finals of the Coppa Italia as Benitez's men overturned a 3-2 first-leg deficit with a comfortable 3-0 win at the Stadio San Paolo on Wednesday.
And the coach went on to praise two of his new signings, Jose Callejon and Gonzalo Higuain, both goalscorers in the second-leg victory over Roma, before predicting that the club would spend again come the end of the season.
"Callejon is working well," he said.
"For me, he is good enough to get in the Spanish national team for the World Cup.
"Higuain has also been an important player for us. He's the sort of lad who needs to feel loved to play well, and he gets that here.
"We'll evaluate what we need in the summer. We have a president who will suddenly invest €100 million, so we have to choose wisely the players we want and the areas we need to improve."
