The 27-year-old was handed a debut for the club as a second-half substitute in Saturday's 2-1 Barclays Premier League defeat at Reading, but Johnson is looking forward to the day when he and leading scorer Steven Fletcher start together.
He told the Sunderland Echo: "I think Danny's a great signing for us.
"He's a quality striker and he just seems to have that knack of getting in the right place at the right time for when the ball drops in the area. He's here to score goals and I'm sure he will.
"You could see the effect he had when he came on in the game against Reading and from a winger's point of view, it's great to have someone to hit in the box.
"Sometimes when you're playing and you have two men around you and one striker in the box with two men around him it's difficult to do anything.
"But when all of a sudden you have two strikers in the box it can make a real difference.
"I've said before to Fletch that when there's just him in the box, it can be so hard to play him in. But when you've got more bodies in the box, you can often really get at teams."