The 28-year-old signed a new four-year contract in August after collecting Liverpool's player of the year award last season and he went on to make 33 appearances in all competitions for the Reds this term.
Napoli's appointment of Benitez has led to a number of Liverpool players being linked with a switch to Serie A but the Slovakian's agent, Karol Csonto, dismissed the idea.
"It's not possible; I consider it a very difficult deal," he told calciomercato.it.
"I like Napoli and I have great respect for this club, but Martin still has a three-year contract with Liverpool and the most likely outcome is that he remains there."
Speaking of Benitez, he said: "They spent three years together, establishing a good relationship with him, but I repeat now that this suggestion is impossible."