Johnson is one of a number of under-performing stars who need to transform their game to revive the Black Cats and haul them to safety.
The former England winger said of the Italian's methods: "It's been a lot different. He's come in and everything has just been turned upside down so quickly, so everyone is still getting used to it. But so far so good, really.
"I think he's probably going to get the best out of the lads and I think he demands the best and obviously we've got to work so hard. That's probably what we need.
"Everybody is very excited.
"He's full of enthusiasm and energy. He just demands the best from his players. I think if you do well for him I think he's going to be a great manager to work for.
"Any time a new manager comes in, people are a little bit stand-off and you don't know how to react.
"Everything happens so quickly. One day you turn up and a new manager turns up. It's difficult, but I'm sure over the course of time everything will fit into."