If we want to be technical, without Johnney, there IS NO Captain Jack. Before Depp was assigned to the role, Jack Sparrow was a very sober, very cool collected man who actually would have ended up a soldier of the British Navy by the end of COTBP, according to "Pirates" From the Magic Kingdom to the Movies"
So, really, no one would be able to fill his gap because the slur, ever drunk Jack would not exits.
