The Liverpool goalkeeper spent last season on loan in Italy, but the Serie A side cannot accommodate his high salary and will now have to "fight for his position" at Anfield
Reina spent last season on loan at Napoli from Liverpool, firmly establishing himself as the Serie A club's number one keeper as they finished third in the league and won the Coppa Italia.
The keeper is keen to return to Napolo permanently with Simon Mignolet now first choice at Anfield, but Benitez has indicated that his compatriot's future does not lie in Naples due to financial issues.
"Pepe has two years left on his contract at Liverpool," the former Valencia, Inter and Chelsea manager told talkSPORT.
"He has to go back and he'll stay there - we can't afford Pepe's wages.
"The Premier League is a very big league and, in Serie A, we don't pay big wages like in England.
"He will have to fight for his position at Liverpool."