Newcastle United have already lost Andros Townsend to Crystal Palace this summer.
Townsend left Newcastle to join Crystal Palace, and although Benitez is under no pressure to sell players, he admits that the club will have to weigh up any offers that they do receive.
Newcastle no longer have the funding that comes with Premier League football, and if valuable offers come in Benitez admits that more players could depart.
"We knew we might lose players, especially Andros because he had a great season and he wanted to play in the Premier League," Benitez said.
"Then you have to react quickly and we were ready. The week before we had two or three signings ready.
"I'm happy with the players that we have and we don't have to sell anybody. Maybe some clubs will come in [with transfer offers] and we will have to analyse each one.”
Newcastle brought in Dwight Gayle, Matt Ritchie and Matz Sels, to cover for the void that Townsend departure has left.
Newcastle wanted to keep Townsend, but they were powerless to resist - as the winger had a release clause in his contract.
The Magpies could now face a fight to keep hold of some of their other key stars.
Both Georginio Wijnaldum and Moussa Sissoko are attracting attention, and could move on this summer.
Newcastle are currently the 2/1 favourites to win the Championship next season.