The Belgium international says the Partenopei boss has asked him to convince his out-of-favour countryman to swap north London for Naples, but admits a move will be tough
Mertens, who moved to the club in June from PSV, claims that Napoli coach Benitez has already asked him to encourage Vermaelen to make the switch to Italy.
Furthermore, Mertens himself wants his international team-mate to move to Napoli, with Vermaelen having fallen out of favour at the Emirates Stadium.
The form of Per Mertesacker and Laurent Koscielny has seen Vermaelen make only two league starts this season with the defender having previously stated a desire to play regularly in the run-up to the World Cup.
"I have already told Vermaelen to come to Napoli 10 times," Mertens told Knack.
"The city is magnificent and even Benitez asked me to convince Vermaelen to come here.
"But Arsenal is a great club and it won't be so easy for him to leave."