Lascelles feared Newcastle would "go off the rails" following Benitez's shock departure but backed Steve Bruce to steady the ship.
"I did think when we came back that it would be quite difficult coming back and not having a manager,' Lascelles said. "I thought players could go off the rails and lose their heads, but they have remained professional.
"(Change) is always difficult as players and this is the first time it has happened to us as a group. We haven't really had any direction.
"The players have to cross the white line and you need heart, passion and desire to be able to do that. Hopefully we can bring a few new faces in as well."