Benitez, whose side sit third in the table, saw his charges move into the final of the Coppa Italia on Wednesday with a 5-3 aggregate win over Roma.
The Italian does not want his charges to let up in their quest to reel in second-placed Roma, with four points currently separating the two.
And he knows that Napoli will need to stave off complacency if they are to avoid an upset against relegation-threatened Sassuolo.
"The players know that against Sassuolo we have the opportunity to continue our battle for second place and make a step forward. It will be a very important game for us," Benitez said.
Alberto Malesani has lost both games since taking charge at the Stadio Citta del Tricolore last month, going down to Verona and Inter.
Benitez is expecting a close game as Sassuolo look to move out of the drop zone after the sides drew 1-1 in September's reverse fixture.
"Sassuolo have changed with a new coach. Back then they were a joyful team who liked to play openly, whereas now they are more focused on getting a result," he continued.
"We also know a coach is never satisfied, so I expect improvements even after our fine performance against Roma."
