"Scott is a one-off. If he goes back to Australia, it's a huge blow for Welsh rugby," said Jones, who has won 55 caps to date.
"He has educated us. When he came over here we were a million miles off things.
"He has broken things down with regards the skill aspects. His technical knowledge is superb and the way he breaks that down and gets it across is second to none."
But since the departure of Mike Ruddock in the week after the win over Scotland, Johnson has been in charge of two disappointing performances.
He is not the man to blame, however, according to British & Irish Lion Jones.
"Everything in the week's preparation leading up to Ireland and Italy was superb, but against Italy we made 22 handling errors - that's nothing to do with coaches, that's down to individual players.
"Coaches shouldn't have to account for players dropping the ball. We as players have to take responsibility for that.
"The coaches have done their side of things but we haven't kept our side of the bargain."
The Clermont Auvergne star number 10 now believes the Wales camp can put aside their recent bad results and pull off what would be a major win over France at the weekend.
"Team spirit is awesome and the work ethic is superb. We have belief in our own ability and we know that if we perform to the best of our ability we can get a result. We genuinely believe that.
"Obviously we are up against a French side who are strong in the set-piece and have some brilliant individuals behind and, as well as that, they had a great victory over England and there is still more to come from them.
"It's going to be a big challenge."