Benitez' men followed their 3-1 triumph over AC Milan last weekend with Wednesday's 3-0 victory against Roma in the Coppa Italia semi-final second leg.
Napoli overturned a 2-1 first-leg deficit and will take on Fiorentina in the final on May 3.
"We played a perfect game against Roma," Benitez said. "We didn't give anything.
"We created so much and, in the end, we were worthy winners. But we have to remain humble and continue to work hard.
"This achievement could help us in the Serie A but we have to remember the league is a different competition.
"Our focus is already on the game at Sassuolo."
Napoli go into the weekend in third place, four points adrift of Roma, although the Giallorossi have a game in hand.
A win at the Citta del Tricolore stadium would be a further boost in conficence in view of Napoli's trip to Wales to face Swansea in Thursday's Europa League last 32 match.
Napoli will not be at full strength on Sunday with midfielders Jorginho and Gokhan Inler as well as striker Jose Maria Callejon all suspended.
Rivals Sassuolo lost 1-0 at Inter Milan last weekend to concede their fourth-straight league loss.
The outcome dropped the Emilia-Romagna club to 19th position, two places and one point adrift of safety.
Despite their poor run of form, Sassuolo coach Alberto Malesani is optimistic his side has the quality to avoid the drop.
"We cannot be depleted," he said. "We are playing well and we just need a victory to turn things around."
Lack of goalscoring has been Sassuolo's main problem with Malesani's outfit having found the back of the net just twice in their last four league games.