Benitez was at pains not to criticise his player in public at his pre-match press conference on Friday afternoon, but admitted only Shelvey, who served a five-match ban last season for racially abusing Wolves player Romain Saiss, could address the problem.
The Spaniard said: "He knows he made a mistake and everyone agrees with that. He is the first one that wants to change, wants to improve. We have been working on that and so is he.
"You cannot predict or prevent it, we are working on that. The situation is not what you are expecting, so you have to keep going to give the right message. At the end it depends on one second when he loses control.
"He knows. It depends on him and those around him."