The former Liverpool shot-stopper says his boss has ensured that the Partenopei go into every game brimming with confidence and self-belief
The Partenopei have made a dream start to the new season, having followed up three successive wins in Serie A with a stirring Champions League triumph over Borussia Dortmund in midweek.
Napoli president Aurelio De Laurentiis splashed plenty of cash during the summer, following the sale of Edinson Cavani to Paris Saint-Germain, but Reina, one of the new arrivals, believes that Benitez is responsible for the club's most important acquisition.
"Benitez has brought a winning mentality to this group and this is very important for us," the former Liverpool shot-stopper told Rai Sport.
"We prepare well for every game and we always go onto the field to win, from the very first minute.
"For us, there is no difference between the Champions League and the Championship. We are just taking it one game at a time.
"We beat Dortmund but now there's Milan, and then Sassuolo. And we will continue like this."
Napoli, who lead Serie A on goal difference from Roma, meet Milan at San Siro at 20:45 on Sunday.