Johnson said: "On Saturday they (Wales) are going to come up against a very, very good side, a side capable of winning the World Cup.
"I don't say that lightly - I think France have more strength in depth than any other side in the world and they have a culture that enables them to play great rugby whilst mixing it too.
"That is why we have a massive task awaiting us in Paris. I know that we played well against Ireland and on another day we might have been talking of a victory rather than a narrow, last-gasp defeat. But let's face it, France in Paris in the springtime is an altogether different prospect."
Wales are hoping to avoid a first Six Nations whitewash and at the same time secure a record-breaking third successive victory in Paris.