Johnson is too inactive for Fury, I think. He'll sit on the ropes and throw too many rounds away. His arrogance means he's one of those fighters who wants to make boxing look like the easiest thing in the world but he's not skilled enough to do it.
If Johnson comes to fight around 243 pounds, his fighting weight, I believe he can make it a difficult night for Fury. In fact, I wouldn't be surprised to see Fury squeak past on a 'dodgy decision'. But of coursel, who knows what sort of shape Johnson is in. These short notice fights can offer up shabby versions of shabby fighters.
Fury will have to be aggressive here, without getting silly. Once Johnson tastes a few jabs he'll shell up all night long