Italia Serie A club Napoli have made an official offer for Chelsea midfielder John Obi Mikel.The offer is believed to be 15 million Euros, according to report on eyefootball.com.The Nigeria international defensive midfielder may now be ready to listen to offers from the Italian club having fallen behind Ramires as first choice holding midfielder at Stamford Bridge, reports the BBC.Napoli manager Rafa Benitez has been busy scouting Europe for new players and has already signed the likes of Pepe Reina and Gonzalo Higuain this summer.Benitez is now ready to raid his former club Chelsea with a move for Mikel. The Blues are believed to be eager to keep their midfielder unless a bid of more than 15 million Euros is received.