Three goals in the opening half hour put Napoli in firm control in Turkey before Duvan Zapata completed the rout in the final minute.
Benitez was delighted with his side's first-leg performance, but refused to get too carried away with the return game only a week away.
"This is a long competition, and that always requires attention and maximum concentration," said the Spaniard.
"You decide your path game by game, and you cannot afford to go wrong ever.
"Anything can happen but you have to always think that the next game is coming, without looking too far into the future.
"We are still in the Europa League and we will try to give it the maximum focus along with our commitments in the league."
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