Kenedy is on-loan at Newcastle from Chelsea.
Benitez, who will hand the 22-year-old the job of unpicking defensively frail visitors Arsenal on Saturday, said: “It is a crucial season for him.
“Obviously he would like to go to Chelsea and win the league, for example. Fine. But it's a win-win situation for us. He has to do really well here if he wants to go there and play and have a chance. They are a top side and it's very demanding. He knows that.
“He will need some time (to get back to his best). His partner was having a baby and it was a difficult time in the summer.
“Hopefully, little by little, it will settle down and he can be the player that we were expecting.
“He has to be consistent. He was doing really well for us for six months, now he has to prove he is someone who can play at this level for a while.
“I think he can do it but he has a difficult summer with the baby. She was in Brazil and in London so it was difficult, but little by little it will settle down.
“He wants to do well and he has to do well."