Just looked in Clareborough's books. There is no Dick (or Richard) Johnson who played for us so Harry Johnson is second from left in the photo. His dad (also Harry) was one of the trainers at the time so it is possible that young Harry had the nickname "Dick" to avoid confusion? Looked in 1921-22 photo and George Richardson looks like the tall chap in the middle, his cap hiding his curly hair. I think the photo was taken before the 1923 FA Cup semi as in these days the Blades often go to the seaside for training before a big cup match. Richardson didnt play in the semi, I think he was a reserve as he played in a league match before the cup tie and in two league matches after.
Correct is From left to right: Tommy Sampy, Harry Johnson, George Richardson, Bill Brelsford, Ernest Milton"