The Magpies recently offloaded winger Andros Townsend to Crystal Palace but quickly replaced him with Bournemouth's Matt Ritchie, while also signing striker Dwight Gayle from Palace and goalkeeper Matz Sels from Gent.
Following their relegation to the Championship, it appeared as though the Toon would be forced to part with a number of their more valued contributors but Benitez has made it clear that the club is not in that situation.
"We knew we might lose players, especially Andros because he had a great season and he wanted to play in the Premier League," Benitez told Sky Sports News HQ.
"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.
"We know it will be very tough for us next season, we have to concentrate on a different division and the motivation has to be there. We have to be ready."