The Belgium international has been linked with an off-season exit from Old Trafford after a disappointing debut season with the English giants.
Fellaini has yet to feature for United during pre-season after being granted extra time off following his World Cup exertions.
New Red Devils boss Louis van Gaal revealed after his side’s US tour that he would be speaking to his players individually about whether they featured in his plans for the upcoming campaign.
Partenopei president Aurelio de Laurentiis confirmed last week that the 26-year-old midfielder was a target for Benitez, who is hoping to trash out a deal if their Premier League counterparts are open to a transfer.
Benitez told the Italian media: “It’s hard not to talk about the transfer market – names keep cropping up constantly. For Fellaini, it’s all down to United, not us.
“In midfield, we’re looking for a player with the right winning mentality. If Fellaini arrives immediately then there won’t be any problem getting him used to our system.
“I have to draw up my list of players for the Champions League so we don’t have much time. He’s not been playing for United so we’ve just got to wait and be respectful.”